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Physics

New submissions

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New submissions for Tue, 20 Feb 18

[1]  arXiv:1802.06074 [pdf, other]
Title: Direct Calculation of the Transfer Map of Electrostatic Deflectors, and Comparison with the Codes $\textit{COSY INFINITY}$ and $\textit{GIOS}$
Comments: 30 pages, 1 figure
Subjects: Accelerator Physics (physics.acc-ph)

COSY INFINITY uses a beamline coordinate system with a Frenet-Serret frame relative to the reference particle, and calculates differential algebra-valued transfer maps by integrating the ODEs of motion in the respective vector space over a differential algebra (DA).
We will describe and perform computation of the DA transfer map of an electrostatic spherical deflector in a laboratory coordinate system using two conventional methods: (1) by integrating the ODEs of motion using a 4th order Runge-Kutta integrator and (2) by computing analytically and in closed form the properties of the respective elliptical orbits from Kepler theory. We will compare the resulting transfer maps with (3) the DA transfer map of COSY INFINITY's built-in electrostatic spherical deflector element ESP and (4) the transfer map of the electrostatic spherical deflector computed using the program GIOS.
In addition to the electrostatic spherical deflector, we study an electrostatic cylindrical deflector, where the Kepler theory is not applicable. We compute the DA transfer map by the ODE integration method (1), and compare it with the transfer maps by (3) COSY INFINITY's built-in electrostatic cylindrical deflector element ECL, and (4) GIOS.
In addition to the code listings in the appendices, the codes to run the test cases are available at this http URL

[2]  arXiv:1802.06076 [pdf, other]
Title: Gamma-ray intensities in multi-gated spectra
Authors: Camille Ducoin (IPNL), Guillaume Maquart (IPNL), Olivier Stézowski (IPNL)
Subjects: Data Analysis, Statistics and Probability (physics.data-an)

The level structure of nuclei offers a large amount and variety of information to improve our knowledge of the strong interaction and of mesoscopic quantum systems. Gamma spectroscopy is a powerful tool to perform such studies: modern gamma multi-detectors present increasing performances in terms of sensitivity and efficiency, allowing to extend ever more our ability to observe and characterize abundant nuclear states. For instance, the high-spin part of level schemes often reflects intriguing nuclear shape phenomena: this behaviour is unveiled by high-fold experimental data analysed through multi-coincidence spectra, in which long deexcitation cascades become observable. Determining the intensity of newly discovered transitions is important to characterize the nuclear structure and formation mechanism of the emitting levels. However, it is not trivial to relate the apparent intensity observed in multi-gated spectra to the actual transition intensity. In this work, we introduce the basis of a formalism affiliated with graph theory: we have obtained analytic expressions from which data-analysis methods can eventually be derived to recover this link in a rigorous way.

[3]  arXiv:1802.06102 [pdf]
Title: Mapping fast evolution of transient surface photovoltage dynamics using G-Mode Kelvin probe force microscopy
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Optoelectronic phenomena in materials such as organic/inorganic hybrid perovskites depend on a complex interplay between light induced carrier generation and fast (electronic) and slower (ionic) processes, all of which are known to be strongly affected by structural inhomogeneities such as interfaces and grain boundaries. Here, we develop a time resolved Kelvin probe force microscopy (KPFM) approach, based on the G-Mode SPM platform, allowing quantification of surface photovoltage (SPV) with microsecond temporal and nanoscale spatial resolution. We demonstrate the approach on methylammonium lead bromide (MAPbBr3) thin films and further highlight the usefulness of unsupervised clustering methods to quickly discern spatial variability in the information rich SPV dataset. Using this technique, we observe concurrent spatial and ultra-fast temporal variations in the SPV generated across the thin film, indicating that structure is likely responsible for the heterogenous behavior.

[4]  arXiv:1802.06106 [pdf]
Title: A deep learning framework for turbulence modeling using data assimilation and feature extraction
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Physics (physics.comp-ph)

Turbulent problems in industrial applications are predominantly solved using Reynolds Averaged Navier Stokes (RANS) turbulence models. The accuracy of the RANS models is limited due to closure assumptions that induce uncertainty into the RANS modeling. We propose the use of deep learning algorithms via convolution neural networks along with data from direct numerical simulations to extract the optimal set of features that explain the evolution of turbulent flow statistics. Statistical tests are used to determine the correlation of these features with the variation in the quantities of interest that are to be predicted. These features are then used to develop improved partial differential equations that can replace classical Reynolds Averaged Navier Stokes models and show improvement in the accuracy of the predictions.

[5]  arXiv:1802.06113 [pdf]
Title: Optics and bremsstrahlung estimates for channeling radiation experiments at FAST
Authors: J. Hyun, P. Piot, T. Sen
Subjects: Accelerator Physics (physics.acc-ph)

This paper presents X-ray spectra of channeling radiation (CR) expected at the FAST (Fermi Accelerator Science and Technology) facility in Fermilab. Our purpose is to produce high brightness quasi-monochromatic X-rays in an energy range from 40 keV to 110 keV. We will use a diamond crystal and low emittance electrons with an energy of around 43 MeV. The quality of emitted X-rays strongly depends on parameters of the electron beam at the crystal. We present simulations of the beam optics for high brightness and high yield operations with bunch charges of 1 pC, 20 pC, and 200 pC. We estimate the X-ray spectra including bremsstrahlung background for a charge of 20 pC. The electron beam distributions with and without channeling in the diamond crystal are calculated. We discuss an X-ray detector system to avoid pile-up effect during high charge operations.

[6]  arXiv:1802.06115 [pdf, ps, other]
Title: On the dissociation between potential vorticity conservation and symmetries
Comments: 11 pages
Subjects: Fluid Dynamics (physics.flu-dyn)

Using a four-dimensional manifestly covariant formalism suitable for classical fluid dynamics, it is shown that the conservation of potential vorticity is not associated with any symmetry of the equations of motion but is instead a trivial conservation law of the second kind. The demonstration is provided in arbitrary coordinates and therefore applies to comoving (or label) coordinates. Since this is at odds with previous studies, which claimed that potential vorticity conservation is associated with a symmetry under particle-relabeling, a detailed discussion on relabeling transformations is also presented.

[7]  arXiv:1802.06133 [pdf, ps, other]
Title: Dual phase-space cascades in 3D hybrid-Vlasov-Maxwell turbulence
Comments: 6 pages, 3 figures, submitted for publication
Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

To explain energy dissipation via turbulence in collisionless, magnetized plasmas, the existence of a dual real- and velocity-space cascade of ion-entropy fluctuations below the ion gyroradius has been proposed. Such a dual cascade, predicted by the gyrokinetic theory, has previously been observed in gyrokinetic simulations of two-dimensional, electrostatic turbulence. For the first time we show evidence for a dual phase-space cascade of ion-entropy fluctuations in a three-dimensional simulation of hybrid-kinetic, electromagnetic turbulence. Energy spectra are largely consistent with a generalized theory for the cascade that accounts for the spectral anisotropy of critically balanced, intermittent, sub-ion-Larmor-scale fluctuations. The observed velocity-space cascade is anisotropic with respect to the magnetic-field direction, with linear phase mixing along magnetic-field lines proceeding mainly at spatial scales above the ion gyroradius and nonlinear phase mixing across magnetic-field lines proceeding at perpendicular scales below the ion gyroradius. Such phase-space anisotropy could be sought in heliospheric and magnetospheric data of solar-wind turbulence.

[8]  arXiv:1802.06134 [pdf]
Title: Towards commissioning the Fermilab Muon G-2 Experiment
Authors: D. Stratakis, M.E. Convery, J.P. Morgan (Fermilab) M.J. Syphers (Fermilab and Northern Illinois U.) M. Korostelev (Lancaster U. and Cockcroft Inst. Accel. Sci. Tech.) A. Fiedler (Northern Illinois U.) S. Kim (Cornell U.) J.D. Crnkovic, W.M. Morse (Brookhaven)
Comments: 4 pp
Subjects: Accelerator Physics (physics.acc-ph); Instrumentation and Detectors (physics.ins-det)

Starting this summer, Fermilab will host a key experiment dedicated to the search for signals of new physics: The Fermilab Muon g-2 Experiment. Its aim is to precisely measure the anomalous magnetic moment of the muon. In full operation, in order to avoid contamination, the newly born secondary beam is injected into a 505 m long Delivery Ring (DR) wherein it makes several revolutions before being sent to the experiment. Part of the commissioning scenario will execute a running mode wherein the passage from the DR will be skipped. With the aid of numerical simulations, we provide estimates of the expected performance.

[9]  arXiv:1802.06136 [pdf, other]
Title: Self-organized oscillations of Leidenfrost drops
Subjects: Fluid Dynamics (physics.flu-dyn)

In the Leidenfrost effect, a thin layer of evaporated vapor forms between a liquid and a hot solid. The complex interactions between the solid, liquid, and vapor phases can lead to rich dynamics even in a single Leidenfrost drop. Here we investigate the self-organized oscillations of Leidenfrost drops that are excited by a constant flow of evaporated vapor beneath the drop. We show that for small Leidenfrost drops, the frequency of a recently reported "breathing mode" can be explained by a simple balance of gravitational and surface tension forces. For large Leidenfrost drops, azimuthal star-shaped oscillations are observed. Our previous work showed how the coupling between the rapid evaporated vapor flow and the vapor-liquid interface excites the star oscillations (Ma \textit{et al., Phys. Rev. Fluids}, 2, 2017, 031602). In our experiments, star-shaped oscillation modes of $n=2$ to 13 are observed in different liquids, the number of observed modes depends sensitively on the liquid viscosity. Here we expand on this work by directly comparing the oscillations with theoretical predictions, and show how the oscillations are initiated by a parametric forcing mechanism through pressure oscillations in the vapor layer. The pressure oscillations are driven by the capillary waves of a characteristic wavelength beneath the drop. These capillary waves can be generated by a large shear stress at the liquid-vapor interface due to the rapid flow of evaporated vapor. We also explore potential effects of thermal convection in the liquid. Although the measured Rayleigh number is significantly larger than the critical value, the frequency (wavelength) of the oscillations depends only on the capillary length of the liquid, and is independent of the drop radius and substrate temperature. Thus convection seems to play a minor role in Leidenfrost drop oscillations, which are mostly hydrodynamic in origin.

[10]  arXiv:1802.06154 [pdf, other]
Title: InP femtosecond mode-locked laser in a compound feedback cavity with a switchable repetition rate
Journal-ref: Optics Letters, Vol. 43, Issue 3, pp. 507-510 (2018)
Subjects: Optics (physics.optics)

A monolithically integrated mode-locked semiconductor laser is proposed. The compound ring cavity is composed of a colliding pulse mode-locking (ML) subcavity and a passive Fabry-Perot feedback subcavity. These two 1.6 mm long subcavities are coupled by using on-chip reflectors at both ends, enabling harmonic mode locking. By changing DC-bias conditions, optical mode spacing from 50 to 450 GHz is experimentally demonstrated. Ultrafast pulses shorter than 0.3 ps emitted from this laser diode are shown in autocorrelation traces.

[11]  arXiv:1802.06158 [pdf, other]
Title: Study of the likelihood of Alfvénic mode bifurcation in NSTX and predictions for ITER baseline scenarios
Subjects: Plasma Physics (physics.plasm-ph)

Rare Alfv\'enic wave transitions between fixed-frequency and chirping phases are identified in NSTX, where Alfv\'enic waves are normally observed to exhibit either chirping or avalanching responses. For those transitions, we apply a criterion [Duarte et al, Nucl. Fusion 57, 054001 (2017)] to predict the nature of fast ion redistribution in tokamaks to be in the convective or diffusive nonlinear regimes. For NSTX discharges in which the transition is not accompanied by changes in the beam deposited power or modifications in the injected radiofrequency power, it has been found that the anomalous fast ion transport is a likely mediator of the bifurcation between the fixed-frequency mode behavior and rapid chirping. For a quantitative assessment, global gyrokinetic simulations of the effects of electrostatic ion temperature gradient turbulence and trapped electron mode turbulence on chirping were pursued using the GTS code. The investigation is extended by means of predictive studies of the probable spectral behavior of Alfv\'enic eigenmodes for baseline ITER cases consisting of elmy, advanced and hybrid scenarios. It has been observed that most modes are found to be borderline between the steady and the chirping phases.

[12]  arXiv:1802.06161 [pdf, other]
Title: Ultracold Rydberg Molecules
Subjects: Atomic Physics (physics.atom-ph)

Ultracold Rydberg molecules have been extensively studied both theoretically and ex-perimentally. Here the authors review the recent realizations of various ultralong-range Rydberg molecules and macrodimers, and explore their potential for current and future applications in spectroscopy, few- and many-body interactions and quantum information processing.

[13]  arXiv:1802.06162 [pdf, other]
Title: Liquid xenon scintillation measurements and pulse shape discrimination in the LUX dark matter detector
Comments: 16 pages, 11 figures
Subjects: Instrumentation and Detectors (physics.ins-det)

Weakly Interacting Massive Particles (WIMPs) are a leading candidate for dark matter and are expected to produce nuclear recoil (NR) events within liquid xenon time-projection chambers. We present a measurement of liquid xenon scintillation characteristics in the LUX dark matter detector and develop a pulse shaped based discrimination parameter to be used for particle identification. To accurately measure the scintillation characteristics, we develop a template-fitting method to reconstruct the detection time of photons. Analyzing calibration data collected during the 2013-16 LUX WIMP search, we measure a singlet-to-triplet scintillation ratio for electron recoils (ER) that is consistent with existing literature, and we make a first-ever measurement of the NR singlet-to-triplet ratio at recoil energies below 74 keV. A prompt fraction discrimination parameter exploits the difference of the photon time spectra for NR and ER events and is optimized to have the least number of ER events that occur in the 50\% NR acceptance region. When this discriminator is used in conjunction with charge-to-light discrimination on the calibration data, the signal-to-noise ratio in the NR dark matter acceptance region increases by up to a factor of two.

[14]  arXiv:1802.06169 [pdf, other]
Title: Role of edge poloidal density asymmetry in tokamak confinement
Authors: A. Y. Aydemir
Comments: 5 pages, 7 figures
Subjects: Plasma Physics (physics.plasm-ph)

Mass flows and radial electric field driven by edge poloidal density asymmetries can be used as a highly effective control mechanism for the edge and thus global confinement in tokamaks. The underlying physics can be demonstrated entirely within a simple magnetohydrodynamic equilibrium model, without resorting to sophisticated and usually collisionality-dependent neoclassical physics arguments. As an example, strong dependence of the low to high (LH) transition power threshold on the magnetic topology, an experimental observation still poorly understood, can be easily explained within this framework. Similar arguments indicate that the ITER fueling ports above the midplane might lead to higher input power requirements.

[15]  arXiv:1802.06187 [pdf, other]
Title: Quenching of stimulated Raman scattering in the kinetic regime by external magnetic fields
Subjects: Plasma Physics (physics.plasm-ph)

We show via particle-in-cell simulations that small normalized magnetic fields ($\omega_c/\omega_p \ll 1$) applied perpendicularly to a light wave can significantly modify the evolution of backward stimulated Raman scattering (SRS) in the kinetic regime. The presence of the magnetic field increases the threshold for kinetic inflation and decreases the amount of reflectivity when SRS is driven significantly above threshold. Analysis indicates this arises because trapped electrons are accelerated as they surf across the wave, leading to the continual dissipation of the electron plasma waves over a wider range of wave amplitudes. The simulation parameters are directly relevant for SRS in inertial confinement fusion devices and indicate that approximately 30 Tesla magnetic fields might significantly reduce SRS backscatter.

[16]  arXiv:1802.06191 [pdf]
Title: Visible and Infrared Organic Polariton Photodiodes
Subjects: Optics (physics.optics); Applied Physics (physics.app-ph); Quantum Physics (quant-ph)

In organic photodiodes (OPDs) light is absorbed by excitons, which dissociate to generate photocurrent. Here, we demonstrate a novel type of OPD in which light is absorbed by polaritons, hybrid light-matter states. We demonstrate polariton OPDs operating in the ultra-strong coupling regime at visible and infrared energies. These devices can be engineered to show narrow responsivity with a very weak angle-dependence. More importantly, they can be tuned to operate outside of the uncoupled absorbance spectrum. Remarkably, we show that the responsivity of a polariton OPD can be pushed to near infrared wavelengths with external quantum efficiencies exceeding those of a control device.

[17]  arXiv:1802.06218 [pdf, other]
Title: Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: effects of shear-thinning and viscoelasticity
Journal-ref: Physics of Fluids 30, 030708 (2018)
Subjects: Computational Physics (physics.comp-ph); Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)

The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a Finite Volume method, at various excitation frequencies. The oil is modelled by the Carreau-Yasuda (CY) and Phan-Thien \& Tanner (PTT) constitutive equations. Both models account for shear-thinning but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from LAOS (Large Amplitude Oscillatory Shear) theory. The CY model also overestimates the damper force relative to the PTT, because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.

[18]  arXiv:1802.06233 [pdf, other]
Title: Persistence and Stochastic Periodicity in the Intensity Dynamics of a Fiber Laser During the Transition to Optical Turbulence
Comments: 10 pages, 13 figures
Subjects: Optics (physics.optics); Chaotic Dynamics (nlin.CD)

Many natural systems display transitions among different dynamical regimes, which are difficult to identify when the data is noisy and high dimensional. A technologically relevant example is a fiber laser, which can display complex dynamical behaviors that involve nonlinear interactions of millions of cavity modes. Here we study the laminar-turbulence transition that occurs when the laser pump power is increased. By applying various data analysis tools to empirical intensity time series we characterize their persistence and demonstrate that at the transition temporal correlations can be precisely represented by a surprisingly simple model.

[19]  arXiv:1802.06242 [pdf, ps, other]
Title: Fully differential cross sections for $ Li^{2+}$-impact ionization of $Li(2s)$ and $Li(2p)$
Comments: 11 pages, 5 Figures
Subjects: Atomic Physics (physics.atom-ph)

A semiclassical impact parameter version of the continuum distorted wave-Eikonal initial state theory is developed to study the differential ionization of $Li$ atoms in collisions with $Li^{2+}$ ions. Both post and prior forms of the transition amplitude are considered. The fully differential cross sections are calculated for the lithium targets in their ground and their first excited states and for the projectile ions at 16~MeV impact energy. The role of the internuclear interaction as well as the significance of the post-prior discrepancy in the ejected electron spectra are investigated. The obtained results for ejection of the electron into the azimuthal plane are compared with the recent measurements and with their corresponding values obtained using a fully quantum mechanical version of the theory. In most of the cases, the consistency of the present approach with the experimental and the quantum theoretical data is reasonable. However, for $2p$-state ionization, in the cases where no experimental data exist, there is a considerable difference between the two theoretical approaches. This difference is questionable and further experiments are needed to judge which theory makes a more accurate description of the collision dynamics.

[20]  arXiv:1802.06245 [pdf, ps, other]
Title: Nonlinear lower-hybrid oscillations in a cold magnetized electron-positron-ion plasma
Subjects: Plasma Physics (physics.plasm-ph)

A new class of the exact nonlinear solutions for the lower-hybrid oscillations in a cold magnetized electron-positron-ion (e-p-i) plasma has been suggested by employing a method of Lagrange variables. It is found that the frequency of the lower-hybrid oscillations in an e-p-i plasma is approximately $\sqrt{3}$ times the frequency of lower-hybrid oscillations in an electron-ion (e-i) plasma. The present work may have some relevance for laboratory/astrophysical e-p-i plasmas.

[21]  arXiv:1802.06256 [pdf]
Title: Spatiotemporal stabilization proof of concept of Broad Area Semiconductor laser sources
Comments: 6 pages, 3 figures
Subjects: Optics (physics.optics)

We provide a numerical proof of concept of a stabilization mechanism for BAS laser sources. The scheme is based on the simultaneous introduction of in-phase two-dimensional modulations on the refractive index and pump (gain). We numerically proof total stabilization in BAS laser sources, both in space and time. We also examine the interplay between the index and gain modulations and the effect of the slow relaxation of carriers on the stabilization performance.

[22]  arXiv:1802.06262 [pdf, other]
Title: Probing Patchy Saturation of Fluids in Nanoporous Media by Ultrasound
Subjects: Geophysics (physics.geo-ph); Applied Physics (physics.app-ph)

Nanoporous materials provide high surface area per unit mass and are capable of fluids adsorption. While the measurements of overall amount of fluid adsorbed by a nanopororus sample are straightforward, probing the fluid spacial distribution is non-trivial. We consider published data on adsorption and desorption of fluids in nanoporous glasses reported along with the measurements of ultrasonic waves propagation. We analyse these using Biot's theory of dynamic poroelasticity, approximating the patches as spherical shells. Our calculations show that on adsorption the patch diameter is on the order of 10-20 pore diameters, while on desorption the patch size is comparable to the sample size. Our analysis suggests that one can employ ultrasound to probe the uniformity of fluid spatial distribution in nanoporous materials.

[23]  arXiv:1802.06276 [pdf, other]
Title: Interactive Estimation of the Fractal Properties of Carbonate Rocks
Subjects: Geophysics (physics.geo-ph)

Scale invariance of intrinsic patterns is an important concept in geology that can be observed in numerous geological objects and phenomena. These geological objects and phenomena are described as containing statistically selfsimilar patterns often modeled with fractal geometry. Fractal geometry has been used extensively to characterize pore space and fracture distribution of both carbonate and clastic rocks as well as the transport properties of porous media and fluid flow in reservoirs. The fractal properties are usually estimated from thin-section photomicrograph images or scanning electron microscope images. For complex rock such as carbonate rocks, automatic feature detection methods are often inaccurate. In addition, the rocks may be have been subjected to facies selective diagenesis which preferentially affect some of the rock fabric, thus increasing the difficulty in automatic detection of certain features. We present an interactive program, GeoBoxCount, for analyzing thin-section images and calculating the fractal dimension interactively. The program relies on the geologists insight in interpreting the features of interest; this significantly improves the accuracy of feature selection. The program provides two options for calculating the fractal dimension: the Hausdorff and the Minkowsi-Bouligand box-counting methods.

[24]  arXiv:1802.06295 [pdf, other]
Title: Resonance line broadened quasilinear (RBQ) model for fast ion distribution relaxation due to Alfvénic eigenmodes
Subjects: Plasma Physics (physics.plasm-ph)

The burning plasma performance is limited by the confinement of the superalfvenic fusion products such as alpha particles and the auxiliary heating ions capable of exciting the Alfv\'enic eigenmodes (AEs). In this work the effect of AEs on fast ions is formulated within the quasi-linear (QL) theory generalized for this problem recently. The generalization involves the resonance line broadened interaction of energetic particles (EP) with AEs supplemented by the diffusion coefficients depending on EP position in the velocity space. A new resonance broadened QL code (or RBQ1D) based on this formulation allowing for EP diffusion in radial direction is built and presented in details. We reduce the wave particle interaction (WPI) dynamics to 1D case when the particle kinetic energy is nearly constant. The diffusion equation for EP distribution evolution is then one dimensional and is solved simultaneously for all particles with the equation for the evolution of the wave angular momentum. The evolution of fast ion constants of motion is governed by the QL diffusion equations which are adapted to find the fast ion distribution function. We make initial applications of the RBQ1D to DIII-D plasma with elevated q-profile where the beam ions show stiff transport properties. AE driven fast ion profile relaxation is studied for validations of the QL approach in realistic conditions of beam ion driven instabilities in DIII-D.

[25]  arXiv:1802.06297 [pdf]
Title: Vortex interaction with a rough wall formed by a hexagonal lattice of posts
Subjects: Fluid Dynamics (physics.flu-dyn)

An experimental study is reported which investigates the head-on collision of a laminar vortex ring of diameter D (Re{\Gamma}= 3000) on a fakir-like surface composed of circular posts of height h*=0.068 located on a planar bed. Lattices of the posts in hexagonal and random distribution (average porosity of e = 0.94 in the layer) are compared to each other with respect to the plain wall. Prior to impact, the vortex ring develops the early state of natural azimuthal instabilities of different mode numbers N=5-7 competing with each other. While impacting with the rough wall, a secondary ring is observed which is pushed outwards and is not wrapped around the primary ring as in flat wall impact. Between both rings of opposite sign vorticity, a strong fluid rebound is induced. The hexagonal lattice causes the rapid growth of further secondary vortex structures in a regular mode number N=6 arrangement at the outer edge of the primary ring in form of six lobes which are aligned with the orientations of preferential pathways in the layer. At the outer tip of the lobes radial wall-jets are generated. Rotating the fakir geometry around the centre of impact also rotates the jets location and direction accordingly. A surface with random lattice of the posts at the same average number density is not able to repeat this observation and no regular secondary flow pattern is visible until full breakdown of the ring. The results show that a tailored arrangement of such posts can be used for near-wall flow control when patterns of preferred pathways in the posts layer lock-on with existing instability modes such as in impacting jet flows or in turbulent boundary layer flows.

[26]  arXiv:1802.06313 [pdf, other]
Title: Deformation of a Half-Space from Anelastic Strain Confined in a Tetrahedral Volume
Authors: Sylvain Barbot
Subjects: Geophysics (physics.geo-ph)

Deformation in the lithosphere-asthenosphere system can be accommodated by faulting and plastic flow. However, incorporating structural data in models of distributed deformation still represents a challenge. Here, I present solutions for the displacements and stress in a half-space caused by distributed anelastic strain confined in a tetrahedral volume. These solutions form the basis of curvilinear meshes that can adapt to realistic structural settings, such as a mantle wedge corner, a spherical shell around a magma chamber, or an aquifer. I provide computer programs to evaluate them in the cases of antiplane strain, plane strain, and three-dimensional deformation. These tools may prove useful in the modeling of deformation data in tectonics, volcanology, and hydrology studies.

[27]  arXiv:1802.06317 [pdf, ps, other]
Title: Spontaneous emission from radiative chiral nematic liquid crystals at the photonic band gap edge: an investigation into the role of the density of photon states near resonance
Comments: 7 Figures, 12 References, 2 Appendices
Journal-ref: Phys. Rev. E 87, 062504 (2013)
Subjects: Optics (physics.optics)

In this article, we investigate the spontaneous emission properties of radiating molecules embedded in a chiral nematic liquid crystal, under the assumption that the electronic transition frequency is close to the photonic edge mode of the structure, i.e. at resonance. We take into account the transition broadening and the decay of electromagnetic field modes supported by the so-called `mirror-less' cavity. We employ the Jaynes-Cummings Hamiltonian to describe the electron interaction with the electromagnetic field, focusing on the mode with the diffracting polarization in the chiral nematic layer. As known in these structures, the density of photon states, calculated via the Wigner method, has distinct peaks on either side of the photonic band gap, which manifests itself as a considerable modification of the emission spectrum. We demonstrate that, near resonance, there are notable differences between the behavior of the density of states and the spontaneous emission profile of these structures. In addition, we examine in some detail the case of the logarithmic peak exhibited in the density of states in 2D photonic structures and obtain analytic relations for the Lamb shift and the broadening of the atomic transition in the emission spectrum. The dynamical behavior of the atom-field system is described by a system of two first order differential equations, solved using the Green's function method and the Fourier transform. The emission spectra are then calculated and compared with experimental data.

[28]  arXiv:1802.06334 [pdf]
Title: New Physics Searches Using Precision Spectroscopy
Authors: Chad Orzel
Comments: Prepared for Advances in Atomic, Molecular, and Optical Physics vol 67
Subjects: Atomic Physics (physics.atom-ph)

The exceptional precision attainable using modern spectroscopic techniques provides a promising avenue to search for signatures of physics beyond the Standard Model in tiny shifts of the energy levels of atoms and molecules. We briefly review three categories of new-physics searches based in precision measurements: tests of QED using measurements of the anomalous magnetic moment of the electron and the value of the fine-structure constant, searches for time variation of the fundamental constants, and searches for a permanent electric dipole moment of an electron or atomic nucleus.

[29]  arXiv:1802.06341 [pdf]
Title: The Mu2e Calorimeter Final Technical Design Report
Authors: N. Atanov (1), V. Baranov (1), J. Budagov (1), S.Ceravolo (2), F. Cervelli (4), F. Colao (2), M. Cordelli (2), G. Corradi (2), E. Dane (2), Y. Davydov (1), S. Di Falco (4), S. Donati (4), E. Diociaiuti (2), R. Donghia (2), B. Echenard (3), K. Flood (3), S. Giovannella (2), V. Glagolev (1), F. Grancagnolo (6), F. Happacher (2), D. Hitlin (3), M. Martini (2), S. Miscetti (2), T. Miyashita (3), L. Morescalchi (4), P. Murat (5), D. Pasciuto (4), G. Pezzullo (4), F. Porter (3), T. Radicioni (4), F. Raffaelli (4), M. Ricci (2), A. Saputi (2), I. Sarra (2), F. Spinella (4), D. Tagnani (2), G. Tassielli (6), V. Tereshchenko (1), Z. Usubov (1), R. Y. Zhu (3) ((1) Joint Institute for Nuclear Research, Dubna, Russia (2) Laboratori Nazionali di Frascati dell INFN, Frascati, Italy (3) California Institute of Technology, Pasadena, United States (4) INFN Sezione di Pisa, Pisa, Italy (5) Fermi National Laboratory, Batavia, Illinois, USA (6) INFN Sezione di Lecce, Lecce, Italy)
Comments: TDR
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)

Since the first version of the Mu2e TDR released at the beginning of 2015, the Mu2e Calorimeter system has undergone a long list of changes to arrive to its final design. These changes were primarily caused by two reasons: (i) the technology choice between the TDR proposed solution of BaF2 crystals readout with solar blind Avalanche Photodiodes (APDs) and the backup option of CsI crystals readout with Silicon Photomultipliers (SiPM) has been completed and (ii) the channels numbering, the mechanical system and the readout electronics were substantially modified while proceeding with engineering towards the final project. This document updates the description of the calorimeter system adding the most recent engineering drawings and tecnical progresses.

[30]  arXiv:1802.06346 [pdf, other]
Title: Design and status of the Mu2e crystal calorimeter
Authors: N. Atanov (1), V. Baranov (1), J. Budagov (1), Yu. I. Davydov (1), V. Glagolev (1), V. Tereshchenko (1), Z. Usubov (1), F. Cervelli (2), S. Di Falco (2), S. Donati (2), L. Morescalchi (2), E. Pedreschi (2), G. Pezzullo (2), F. Raffaelli (2), F. Spinella (2), F. Colao (3), M. Cordelli (3), G. Corradi (3), E. Diociaiuti (3), R. Donghia (3), S. Giovannella (3), F. Happacher (3), M. Martini (3), S. Miscetti (3), M. Ricci (3), A. Saputi (3), I. Sarra (3), B. Echenard (4), D. G. Hitlin (4), T. Miyashita (4), F. Porter (4), R. Y. Zhu (4), F. Grancagnolo (5), G. Tassielli (5), P.Murat (6) ((1) Joint Institute for Nuclear Research, Dubna, Russia (2) INFN Sezione di Pisa, Pisa, Italy (3) Laboratori Nazionali di Frascati dell'INFN, Frascati, Italy (4) California Institute of Technology, Pasadena, United States (5) INFN Sezione di Lecce, Lecce, Italy (6) Fermi National Laboratory, Batavia, Illinois, USA)
Comments: 8 pages, 16 figures, submitted to IEEE
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)

The Mu2e experiment at Fermilab searches for the charged-lepton flavour violating (CLFV) conversion of a negative muon into an electron in the field of an aluminum nucleus, with a distinctive signature of a mono-energetic electron of energy slightly below the muon rest mass (104.967 MeV). The Mu2e goal is to improve by four orders of magnitude the search sensitivity with respect to the previous experiments. Any observation of a CLFV signal will be a clear indication of new physics. The Mu2e detector is composed of a tracker, an electro- magnetic calorimeter and an external veto for cosmic rays surrounding the solenoid. The calorimeter plays an important role in providing particle identification capabilities, a fast online trigger filter, a seed for track reconstruction while working in vacuum, in the presence of 1 T axial magnetic field and in an harsh radiation environment. The calorimeter requirements are to provide a large acceptance for 100 MeV electrons and reach at these energies: (a) a time resolution better than 0.5 ns; (b) an energy resolution < 10% and (c) a position resolution of 1 cm. The calorimeter design consists of two disks, each one made of 674 undoped CsI crystals read by two large area arrays of UV-extended SiPMs. We report here the construction and test of the Module-0 prototype. The Module-0 has been exposed to an electron beam in the energy range around 100 MeV at the Beam Test Facility in Frascati. Preliminary results of timing and energy resolution at normal incidence are shown. A discussion of the technical aspects of the calorimeter engineering is also reported in this paper.

[31]  arXiv:1802.06348 [pdf, other]
Title: Quantitative Predictions in Quantum Decision Theory
Comments: Latex file, 17 pages, 1 figure
Journal-ref: IEEE Trans. Syst. Man Cybern. Syst. 48 (2018) 366-381
Subjects: Physics and Society (physics.soc-ph); Quantum Physics (quant-ph)

Quantum Decision Theory, advanced earlier by the authors, and illustrated for lotteries with gains, is generalized to the games containing lotteries with gains as well as losses. The mathematical structure of the approach is based on the theory of quantum measurements, which makes this approach relevant both for the description of decision making of humans and the creation of artificial quantum intelligence. General rules are formulated allowing for the explicit calculation of quantum probabilities representing the fraction of decision makers preferring the considered prospects. This provides a method to quantitatively predict decision-maker choices, including the cases of games with high uncertainty for which the classical expected utility theory fails. The approach is applied to experimental results obtained on a set of lottery gambles with gains and losses. Our predictions, involving no fitting parameters, are in very good agreement with experimental data. The use of quantum decision making in game theory is described. A principal scheme of creating quantum artificial intelligence is suggested.

[32]  arXiv:1802.06356 [pdf, other]
Title: Lamellar ordering, droplet formation and phase inversion in exotic active emulsions
Comments: 15 pages: Manuscprit (4 figures) and SI (11 figures)
Subjects: Biological Physics (physics.bio-ph); Soft Condensed Matter (cond-mat.soft)

We study numerically the behaviour of a mixture of a passive isotropic fluid and an active polar gel, in the presence of a surfactant favouring emulsification. Focussing on parameters for which the underlying free energy favours the lamellar phase in the passive limit, we show that the interplay between nonequilibrium and thermodynamic forces creates a range of multifarious exotic emulsions. When the active component is contractile (e.g., an actomyosin solution), moderate activity enhances the efficiency of lamellar ordering, whereas strong activity favours the creation of passive droplets within an active matrix. For extensile activity (occurring, e.g., in microtubule-motor suspensions), instead, we observe an emulsion of spontaneously rotating droplets of different size. By tuning the overall composition, we can create high internal phase emulsions, which undergo sudden phase inversion when activity is switched off. Therefore, we find that activity provides a single control parameter to design composite materials with a strikingly rich range of morphologies.

[33]  arXiv:1802.06362 [pdf]
Title: Experimental demonstration of three-dimensional broadband underwater acoustic carpet cloak
Subjects: Applied Physics (physics.app-ph)

We present the design, architecture and detailed performance of a three-dimensional (3D) underwater acoustic carpet cloak (UACC). The proposed system of the 3D UACC is an octahedral pyramid which is composed of periodical steel strips. This underwater acoustic device, placed over the target to hide, is able to manipulate the scattered wavefront to mimic a reflecting plane. The effectiveness of the prototype is experimentally demonstrated in an anechoic tank. The measured acoustic pressure distributions show that the 3D UACC can work in all directions in a wide frequency range. This experimental verification of 3D device paves the way for guidelines on future practical applications.

[34]  arXiv:1802.06417 [pdf, other]
Title: Superthermal photon bunching in terms of simple probability distributions
Subjects: Optics (physics.optics); Quantum Physics (quant-ph)

We analyze the second-order photon autocorrelation function $g^{(2)}$ with respect to the photon probability distribution and discuss the generic features of a distribution that result in superthermal photon bunching ($g^{(2)}>2$). Superthermal photon bunching has been reported for a number of optical microcavity systems that exhibit processes like superradiance or mode competition. We show that a superthermal photon number distribution cannot be constructed from the principle of maximum entropy, if only the intensity and the second-order autocorrelation are given. However, for bimodal systems an unbiased superthermal distribution can be constructed from second-order correlations and the intensities alone. Our findings suggest modeling superthermal single-mode distributions by a mixture of a thermal and a lasing like state and thus reveal a generic mechanism in the photon probability distribution responsible for creating superthermal photon bunching. We relate our general considerations to a physical system, a (single-emitter) bimodal laser, and show that its statistics can be approximated and understood within our proposed model. Furthermore the excellent agreement of the statistics of the bimodal laser and our model reveal that the bimodal laser is an ideal source of bunched photons, in the sense that it can generate statistics that contain no other features but the superthermal bunching.

[35]  arXiv:1802.06420 [pdf, ps, other]
Title: Spectral stability of nonlinear gravity waves in the atmosphere
Subjects: Fluid Dynamics (physics.flu-dyn)

We apply spectral stability theory to investigate nonlinear gravity waves in the atmosphere. These waves are described by modulation equations being derived from nonlinear Wentzel-Kramers-Brillouin theory. First, we establish that plane waves, which represent exact solutions to the inviscid Boussinesq equations, are spectrally stable with respect to their nonlinear modulation equations under the same conditions as what is known as modulational stability from weakly nonlinear theory. Second, we show that traveling waves solving the inviscid modulation equations that compare to pseudo-incompressible theory, which accounts in contrast to Boussinesq for the altitudinal varying background density, are unconditionally unstable. Both inviscid regimes turn out to be ill-posed. A regularization is found by including dissipative effects. The according traveling wave packets generate transient essential instabilities that decay locally at every fixed point if the wave packet travels downwards or if the wave packet travels upwards and the group velocity, as defined by the derivative of the frequency, does not exceed the envelope velocity at no point. Additionally, all three types of nonlinear modulation equations are solved numerically to further investigate the nature of the analytic stability results.

[36]  arXiv:1802.06421 [pdf, other]
Title: Measuring Accessibility using Gravity and Radiation Models
Comments: 12 Pages, 4 Figures
Subjects: Physics and Society (physics.soc-ph)

Since the presentation of the Radiation Model, much work has been done to compare its findings with those obtained from Gravitational Models. These comparisons always aim at measuring the accuracy with which the models reproduce the mobility described by origin-destination matrices. This has been done at different spatial scales using different datasets, and several versions of the models have been proposed to adjust to various spatial systems. However the models, to our knowledge, have never been compared with respect to policy testing scenarios. For this reason, here we use the models to analyze the impact of the introduction of a new transportation network, a Bus Rapid Transport system, in the city of Teresina in Brazil. We do this by measuring the estimated variation in the trip distribution, and formulate an accessibility to employment indicator for the different zones of the city. By comparing the results obtained with the two approaches, we are able, not only to better assess the goodness of fit and the impact of this intervention, but also to understand reasons for the systematic similarities and differences in their predictions.

[37]  arXiv:1802.06423 [pdf, other]
Title: Experimental investigation of dynamical structures formation due to flowing complex plasma past an obstacle
Comments: 9 pages, 7 figures
Subjects: Plasma Physics (physics.plasm-ph)

We report the experimental observation of dynamical behavior of flowing complex plasma past a spherical obstacle. The experiment has been carried out in a $\Pi$-shaped DC glow discharge experimental device using kaolin particles as the dust component in a background of Argon plasma. A stationary dust cloud is formed by maintaining the pumping speed and gas flow rate. A spherical obstacle vertically mounted on the cathode tray acts as an obstacle to the flow of dust particles. The controlled dust flow is generated by reducing the mass flow of the neutrals through a mass flow controller. The flowing dust particles are repelled by the electrostatic field of the negatively charged sphere and a microparticle free region (dust void) is formed surrounding the obstacle. The far particles are attracted towards the floating obstacle and reflected back when they have arrived at a minimum distance, causing a ring shaped structure around the obstacle. We characterize the shape of this structure over a range of dust flow speeds and obstacle biases. For a supersonic flow of dust fluid around a negatively biased obstacle, a bow shock is formed on the upstream side of the sphere, while the generation of wave structures is observed on the downstream side for a particular range of flow velocities. Reynolds numbers in this case is estimated as $R_e \gtrsim 50$. This wave structure reminds of the beginning of the formation of a Von-K\'arm\'an vortex street. A physical picture for the observed structure based on ion-drag, neutral streaming and electric forces is discussed.

[38]  arXiv:1802.06448 [pdf, other]
Title: Particle resuspension from complex surfaces: current knowledge and limitations
Authors: Christophe Henry
Subjects: Fluid Dynamics (physics.flu-dyn); Soft Condensed Matter (cond-mat.soft)

This review explores particle resuspension from surfaces due to fluid flows. The objective of this review is to provide a general framework and terminology for particle resuspension while highlighting the future developments needed to deepen our understanding of these phenomena. For that purpose, the manuscript is organized with respect to three mechanisms identified in particle resuspension, namely: the incipient motion of particles (i.e. how particles are set in motion), their migration on the surface (i.e. rolling or sliding motion) and their re-entrainment in the flow (i.e. their motion in the near-wall region after detachment). Recent measurements and simulations of particle resuspension are used to underline our current understanding of each mechanism for particle resuspension. These selected examples also highlight the limitations in the present knowledge of particle resuspension, while providing insights into future developments that need to be addressed. In particular, the paper addresses the issue of adhesion forces between complex surfaces - where more detailed characterizations of adhesion force distributions are needed - and the issue of particle sliding/rolling motion on the surface - which can lead to particles halting/being trapped in regions with high adhesion forces.

[39]  arXiv:1802.06468 [pdf, other]
Title: Fast synthetic CT generation with deep learning for general pelvis MR-only Radiotherapy
Comments: Submitted to Physics in Medicine and Biology
Subjects: Medical Physics (physics.med-ph)

To enable magnetic resonance (MR)-only radiotherapy and facilitate modelling of radiation attenuation in humans, synthetic CT (sCT) images need to be generated. Considering the application of MR-guided radiotherapy, sCT generation should occur within minutes. This work aims at assessing whether an existing deep learning network can rapidly generate sCT images leading to accurate MR-based dose calculations in the entire pelvis. A study was conducted on data of 91 patients with prostate (59), rectal (18) and cervical (14) cancer who underwent external beam radiotherapy acquiring both CT and MRI for patients' simulation. Dixon reconstructed water, fat and in-phase images obtained from a conventional dual gradient-recalled echo sequence were used to generate sCT images. A conditional generative adversarial network (cGAN) was used to generate sCT images. The network was trained in a paired fashion on 2D transverse slices of 32 prostate patients and feed-forward evaluated on the remaining patients (test set). For 30 patients in the test set, dose recalculations of the clinical plan were performed on sCT images. Dose distributions were evaluated comparing voxel-based dose differences, gamma and dose-volume histogram (DVH) analysis. The sCT generation required 5.6s and 21s for a single patient volume on a GPU and CPU, respectively. On average, sCT images resulted in a higher dose to the target of maximum 0.3%. The average gamma pass rates using the 3%,3mm and 2%,2mm criteria were above 97 and 91%, respectively, for all volumes of interests considered. All DVH points from the sCT-based plans differed less than $\pm$2.5% from the corresponding points on CT-based plans. Results suggest that accurate MR-based dose calculation using sCT images generated with a cGAN is feasible for the entire pelvis. The sCT generation was sufficiently fast to be integrated into an MR-guided radiotherapy workflow.

[40]  arXiv:1802.06500 [pdf]
Title: The Initial Approximations for Achromatic Doublets of the XVIII Century
Authors: Igor Nesterenko
Comments: 16 pages, 8 figures, 4 tables
Subjects: History and Philosophy of Physics (physics.hist-ph)

Analysis of the both type (flint-forward and crown-forward) achromatic doublets was carried out. The investigation revealed possible initial approximations which could be used by opticians at producing of the achromatic doublets in last half of XVIII century. The comparative analysis of approximate versions of achromatic doublets has provided additional explanation to some historical events. One more confirmation that the earliest achromatic doublets were really flint-forward type was found.

[41]  arXiv:1802.06540 [pdf, other]
Title: Generalized perspective on chiral measurements without magnetic interactions
Subjects: Atomic Physics (physics.atom-ph); Atomic and Molecular Clusters (physics.atm-clus); Chemical Physics (physics.chem-ph); Optics (physics.optics); Quantum Physics (quant-ph)

We present a unified description of several methods of chiral discrimination based on electric-dipole interactions. It includes photoelectron circular dichroism (PECD), microwave rotational enantio-sensitive spectroscopy, photoexcitation circular dichroism (PXCD) and photoelectron photoexcitation circular dichroism (PXECD). We show that, inspite of the fact that the physics underlying the appearance of a chiral response is very different in all these methods, the chiral observable in all cases has a unique form. It is a polar vector given by the product of (i) the molecular pseudoscalar and (ii) the field pseudovector specified by configurations of the electromagnetic fields interacting with an isotropic ensemble of chiral molecules. The molecular pseudoscalar is a rotationally invariant property, which is composed from different molecule-specific vectors and in the simplest case is a triple product of such vectors. The key property that enables the chiral response is the non coplanarity of the vectors forming such triple product. The key property that enables chiral detection without using chiral electromagnetic fields is the vectorial nature of the enantio-sensitive observable. Our compact and general expression for this observable shows what ultimately determines the efficiency of the chiral signal and if, or when, it can reach 100%. We also discuss the differences between the two phenomena, which rely on the bound states, PXCD and microwave enantio-sensitive spectroscopy, and the two phenomena using the continuum states, PECD and PXECD. Finally, we extend these methods to arbitrary polarizations of electromagnetic fields used to induce and probe the chiral response.

[42]  arXiv:1802.06542 [pdf, ps, other]
Title: Seismic Cross-coupling Noise in Torsion Pendulums
Comments: 9 pages, 12 figures
Subjects: Instrumentation and Detectors (physics.ins-det)

Detection of low frequency gravitational waves around 0.1 Hz is one of the important targets for future gravitational wave observation. One of the main sources of the fluctuation is gravitational waves from binary intermediate-mass black hole coalescences which is proposed as one of the formation scenarios of supermassive black holes. By using a torsion pendulum, which can have a resonance frequency of a few millihertz, such perturbation can be measured on the ground since its rotational motion can act as a free mass down to 0.01 Hz. However, sensitivity of a realistic torsion pendulum will suffer from torsional displacement noise introduced from translational ground motion in the main frequency band of interest. Such noise is called seismic cross-coupling noise and there have been little research on it. In this paper, systematic investigation is performed to identify routes of cross-coupling transfer for standard torsion pendulums. Based on the results this paper also proposes reduction schemes of cross-coupling noise, and they were demonstrated experimentally in agreement with theory. This result establishes a basic way to reduce seismic noise in torsion pendulums.

[43]  arXiv:1802.06544 [pdf]
Title: Templated ligation can create a hypercycle replication network
Comments: 32 pages, 18 figures
Subjects: Biological Physics (physics.bio-ph); Biomolecules (q-bio.BM)

The stability of sequence replication was crucial for the emergence of molecular evolution and early life. Exponential replication with a first-order growth dynamics show inherent instabilities such as the error catastrophe and the dominance by the fastest replicators. This favors less structured and short sequences. The theoretical concept of hypercycles has been proposed to solve these problems. Their higher-order growth kinetics leads to frequency-dependent selection and stabilizes the replication of majority molecules. However, many implementations of hypercycles are unstable or require special sequences with catalytic activity. Here, we demonstrate the spontaneous emergence of higher-order cooperative replication from a network of simple ligation chain reactions (LCR). We performed long-term LCR experiments from a mixture of sequences under molecule degrading conditions with a ligase protein. At the chosen temperature cycling, a network of positive feedback loops arose from both the cooperative ligation of matching sequences and the emerging increase in sequence length. It generated higher-order replication with frequency-dependent selection. The experiments matched a complete simulation using experimentally determined ligation rates and the hypercycle mechanism was also confirmed by abstracted modeling. Since templated ligation is a most basic reaction of oligonucleotides, the described mechanism could have been implemented under microthermal convection on early Earth.

[44]  arXiv:1802.06548 [pdf, other]
Title: Level Zero Trigger Processor for the NA62 experiment
Comments: 14 pages
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)

The NA62 experiment is designed to measure the ultra-rare decay $K^+ \rightarrow \pi^+ \nu \bar{\nu}$ branching ratio with a precision of $\sim 10\%$ at the CERN Super Proton Synchrotron (SPS). The L0 Trigger Processor (L0TP) is the lowest level system of the trigger chain. It is hardware implemented using programmable logic. The architecture of the L0TP is completely new for a high energy physics experiment. It is fully digital, based on a standard gigabit Ethernet communication between detectors and L0TP Board. The L0TP Board is a commercial development board, mounting a programmable logic device (FPGA). The primitives generated by sub-detectors are sent asynchronously using the UDP protocol to the L0TP during the entire beam spill period. The L0TP realigns in time the primitives coming from seven different sources and performs a data selection based on the characteristics of the event such as energy, multiplicity and topology of hits in the sub-detectors. It guarantees a maximum latency of 1 ms. The maximum input rate is about 10 MHz for each sub-detector, while the design maximum output trigger rate is 1 MHz. A description of the trigger algorithm is presented here.

[45]  arXiv:1802.06556 [pdf, ps, other]
Title: Plasma boosted electron beams for driving Free Electron Lasers
Comments: 5 pages, 2 figures
Subjects: Accelerator Physics (physics.acc-ph)

In this paper, we report results of simulations, in the framework of both EuPRAXIA \cite{Walk2017} and EuPRAXIA@SPARC\_LAB \cite{Ferr2017} projects, aimed at delivering a high brightness electron bunch for driving a Free Electron Laser (FEL) by employing a plasma post acceleration scheme. The boosting plasma wave is driven by a tens of \SI{}{\tera\watt} class laser and doubles the energy of an externally injected beam up to \GeV{1}. The injected bunch is simulated starting from a photoinjector, matched to plasma, boosted and finally matched to an undulator, where its ability to produce FEL radiation is verified to yield $O(\num{e11})$ photons per shot at \nm{2.7}.

[46]  arXiv:1802.06557 [pdf]
Title: Symmetry and Contextuality
Authors: Hartmann Römer
Comments: 8 pages, contribution to the interdisciplinary workshop "Symmetry and Seriality" of the Freiburg Institute of Advanced Studies (FRIAS), May 2016
Subjects: History and Philosophy of Physics (physics.hist-ph)

The general concept of symmetry is realized in manifold ways in different realms of reality, such as plants, animals, minerals, mathematical objects or human artefacts in literature, fine arts and society. In order to arrive at a common ground for this variedness a very general conceptualization of symmetry is proposed: Existence of substitutions, which, in the given context, do not lead to an essential change. This simple definition has multiple consequences: -The context dependence of the notion of symmetry is evident in the humanities but by no means irrelevant yet often neglected in science. The subtle problematic of concept formation and the ontological status of similarities opens up. -In general, the substitutions underlying the concept of symmetry are not really performed but remain in a state of virtuality. Counterfactuality, freedom and creativity come into focus. The detection of previously hidden symmetries may provide deep and surprising insights. -Related to this, due attention is devoted to the aesthetic dimension of symmetry and the breaking of it. -Finally, we point out to what extent life is based on the interplay between order and freedom, between full and broken symmetry.

[47]  arXiv:1802.06562 [pdf, other]
Title: CUPID-0: the first array of enriched scintillating bolometers for 0νββdecay investigations
Subjects: Instrumentation and Detectors (physics.ins-det)

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of $^{82}$Se neutrinoless double-beta decay (0$\nu\beta\beta$). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0$\nu\beta\beta$ at the level of 10$^{-3}$ c/keV/kg/y, the lowest value ever measured using cryogenic detectors. This result can be achieved by a state of the art technology for background suppression and thorough protocols and procedures for detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising detector performance which are here preliminarily discussed

[48]  arXiv:1802.06584 [pdf, other]
Title: High precision wavefront control in Point Spread Function engineering for single emitter localization
Subjects: Optics (physics.optics)

Point Spread Function (PSF) engineering is used in single emitter localization to measure the emitter position in 3D and possibly other parameters such as the emission color or dipole orientation as well. Advanced PSF models such as spline fits to experimental PSFs or the vectorial PSF model can be used in the corresponding localization algorithms in order to model the intricate spot shape and deformations correctly. The complexity of the optical architecture and fit model makes PSF engineering approaches particularly sensitive to optical aberrations. Here, we present a calibration and alignment protocol for fluorescence microscopes equipped with a Spatial Light Modulator with the goal of establishing a wavefront error well below the diffraction limit for optimum application of complex engineered PSFs. We achieve high-precision wavefront control, to a level below 20 m$\lambda$ wavefront aberration over a 30 minute time window after the calibration procedure, using a separate light path for calibrating the pixel-to-pixel variations of the SLM, and alignment of the SLM with respect to the optical axis and Fourier plane within 3 $\mu$m ($x/y$) and 100 $\mu$m ($z$) error. Aberrations are retrieved from a fit of the vectorial PSF model to a bead $z$-stack and compensated with a residual wavefront error comparable to the error of the SLM calibration step. This well-calibrated and corrected setup makes it possible to create complex `3D+$\lambda$' PSFs that fit very well to the vectorial PSF model. Proof-of-principle bead experiments show precisions below 10~nm in $x$, $y$, and $\lambda$, and below 20~nm in $z$ over an axial range of 1 $\mu$m with 2000 signal photons and 12 background photons.

[49]  arXiv:1802.06590 [pdf, ps, other]
Title: Geomagnetic storm forecasting service StormFocus: 5 years online
Comments: 22 pages, 8 figures, 3 tables, accepted for publication in Journal of Space Weather and Space Climate
Subjects: Space Physics (physics.space-ph)

Forecasting geomagnetic storms is highly important for many space weather applications. In this study we review performance of the geomagnetic storm forecasting service StormFocus during 2011--2016. The service was implemented in 2011 at SpaceWeather.Ru and predicts the expected strength of geomagnetic storms as measured by $Dst$ index several hours ahead. The forecast is based on L1 solar wind and IMF measurements and is updated every hour. The solar maximum of cycle 24 is weak, so most of the statistics are on rather moderate storms. We verify quality of selection criteria, as well as reliability of real-time input data in comparison with the final values, available in archives. In real-time operation 87% of storms were correctly predicted while the reanalysis running on final OMNI data predicts successfully 97% of storms. Thus the main reasons for prediction errors are discrepancies between real-time and final data (Dst, solar wind and IMF) due to processing errors, specifics of datasets.

[50]  arXiv:1802.06599 [pdf, other]
Title: Study of Rydberg blockade in thermal vapor
Subjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)

We present the experimental demonstration of Rydberg blockade in thermal atomic vapor where the atoms are not necessarily be frozen. We show that not all the interacting atoms but only the atoms with same velocity collectively participate in the blockade process. Using this observation, we formulated a suitable model based on super atom picture to study blockade interaction in thermal vapor. We performed an experiment to measure Rydberg population in rubidium thermal vapor using optical heterodyne detection technique and density dependent suppression of Rydberg population is observed in suitable experimental parameter regime. Further analysis of the experimental data using the model verifies the scaling law for van der Waals interaction strength $(C_{6})$ with principal quantum number of the Rydberg state with $11\%$ error. Our result suggests multi-photon excitation in thermal vapor with suitable laser configuration to probe Rydberg blockade interaction based optical nonlinearity and many body effects.

[51]  arXiv:1802.06600 [pdf, other]
Title: Ultrafast perturbation maps as a quantitative tool for testing of multi-port photonic devices
Subjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Advanced photonic probing techniques are of great importance for the development of non-contact wafer-scale testing of photonic chips. Ultrafast photomodulation has been identified as a powerful new tool capable of remotely mapping photonic devices through a scanning perturbation. Here, we develop photomodulation maps into a quantitative technique through a general and rigorous method based on Lorentz reciprocity that allows the prediction of transmittance perturbation maps for arbitrary linear photonic systems with great accuracy and minimal computational cost. Excellent agreement is obtained between predicted and experimental maps of various optical multimode-interference devices, thereby allowing direct comparison of a device under test with a physical model of an ideal design structure. In addition to constituting a promising route for optical testing in photonics manufacturing, ultrafast perturbation mapping may be used for design optimization of photonic structures with reconfigurable functionalities.

[52]  arXiv:1802.06612 [pdf, other]
Title: Nonlinear Breit-Wheeler pair creation with bremsstrahlung $γ$ rays
Comments: 12 pages, 5 figures
Subjects: Plasma Physics (physics.plasm-ph); High Energy Physics - Phenomenology (hep-ph)

Electron-positron pairs are produced through the Breit-Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-$Z$ target is used to produce $\gamma$ rays that collide with a counterpropagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit-Wheeler positrons, and verify our analytical predictions with simulations of the cascade in the material and in the laser pulse. The electron beam energy and laser intensity required are well within the capability of today's high-intensity laser facilities.

[53]  arXiv:1802.06616 [pdf]
Title: Suppression of photo-oxidation of organic chromophores by strong coupling to plasmonic nanoantennas
Comments: 5 figures; includes Supplementary Materials
Subjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Chemical Physics (physics.chem-ph)

Intermixed light-matter quasiparticles - polaritons - possess unique optical properties owned to their compositional nature. These intriguing hybrid states have been extensively studied over the past decades in a wide range of realizations aiming at both basic science and emerging applications. However, recently it has been demonstrated that not only optical, but also material-related properties, such as chemical reactivity and charge transport, may be significantly altered in the strong coupling regime of light-matter interactions. Here, we show that a nanoscale system, comprised of a plasmonic nanoprism strongly coupled to excitons in J-aggregated form of organic chromophores, experiences modified excited state dynamics and therefore modified photo-chemical reactivity. Our experimental results reveal that photobleaching, one of the most fundamental photochemical reactions, can be effectively controlled and suppressed by the degree of plasmon-exciton coupling and detuning. In particular, we observe a 100-fold stabilization of organic dyes for the red-detuned nanoparticles. Our findings contribute to understanding of photochemical properties in the strong coupling regime and may find important implications for the performance and improved stability of optical devices incorporating organic dyes.

[54]  arXiv:1802.06622 [pdf, other]
Title: Setting the clock of photoelectron emission through molecular alignment
Subjects: Atomic Physics (physics.atom-ph); Atomic and Molecular Clusters (physics.atm-clus); Chemical Physics (physics.chem-ph)

The interaction of strong laser fields with matter intrinsically provides powerful tools to image transient dynamics with an extremely high spatiotemporal resolution. In strong-field physics, the initial conditions of this interaction are generally considered a weak perturbation. We investigated strong-field ionisation of laser-aligned molecules and showed, for the first time, that the initial momentum acquired by the photoelectron at birth has a dramatic impact on the overall strong-field dynamics: It sets the clock for the emission of electrons with a given kinetic energy. This result represents a new benchmark for the seminal statements of strong-field physics, highlighting the crucial importance of the initial electron-emission conditions. Our findings have strong impact on the interpretation of self-diffraction experiments, where the photoelectron momentum distribution is used to retrieve molecular structures. Furthermore, the resulting encoding of the time-energy relation in molecular-frame photoelectron distributions provides a new way of probing the molecular potential with sub-femtosecond resolution and accessing a deeper understanding of electron tunnelling.

[55]  arXiv:1802.06630 [pdf]
Title: Ultrafast Preparation and Detection of Ring Currents in Single Atoms
Comments: 19 pages, 6 figures, Nature Physics accepted
Subjects: Atomic Physics (physics.atom-ph)

Quantum particles can penetrate potential barriers by tunneling (1). If that barrier is rotating, the tunneling process is modified (2,3). This is typical for electrons in atoms, molecules or solids exposed to strong circularly polarized laser pulses (4,5). Here we measure how the transmission probability through a rotating tunnel depends on the sign of the magnetic quantum number m of the electron and thus on the initial sense of rotation of its quantum phase. We further show that the electron keeps part of that rotary motion on its way through the tunnel by measuring m-dependent modification of the electron emission pattern. These findings are relevant for attosecond metrology as well as for interpretation of strong field electron emission from atoms and molecules (6-13) and directly demonstrates the creation of ring currents in bound states of ions with attosecond precision. In solids, this could open a way to inducing and controlling ring-current related topological phenomena (14).

[56]  arXiv:1802.06632 [pdf]
Title: Large Scale Liquid Metal Batteries
Subjects: Applied Physics (physics.app-ph); Fluid Dynamics (physics.flu-dyn)

Liquid metal batteries are possible candidates for large scale energy storage offering a possible breakthrough of intermittent wind and solar energy exploitations. The major concern over their practical implementation is the operation at elevated temperatures and sensitivity to liquid motion. The concept of liquid metal battery bears a close similarity to aluminium electrolytic production cells. The two liquid layer MHD effects can be projected to the three liquid layer self-segregated structure of the batteries. This paper presents numerical models for the three density-stratified electrically conductive liquid layers using 3D and shallow layer approximation accounting for specific MHD effects during periods of battery activity. It is demonstrated that a stable operation of these batteries can be achieved if reusing an infrastructure of existing aluminium electrolysis pot lines. The basic principles of the MHD processes in the cells are illustrated by the numerical example cases.

[57]  arXiv:1802.06635 [pdf]
Title: Optical tristability and ultrafast Fano switching in nonlinear magneto-plasmonic nanoparticles
Comments: 13 pages, 6 figures
Subjects: Optics (physics.optics); Adaptation and Self-Organizing Systems (nlin.AO)

We consider light scattering by a coated magneto-plasmonic nanoparticle (MPNP) with a Kerr-type nonlinear plasmonic shell and a magneto-optic core. Such structure features two plasmon dipole modes, associated with electronic oscillations on the inner and outer surfaces of the shell. Driven in a nonlinear regime, each mode exhibits a bistable response. Bistability of an inner plasmon leads to switching between this state and a Fano resonance (Fano switching). Once the external light intensity exceeds the critical value, the bistability zones of both eigen modes overlap yielding optical tristability characterized by three stable steady states for a given wavelength and light intensity. We develop a dynamic theory of transitions between nonlinear steady states and estimate the characteristic switching time as short as 0.5 ps. We also show that the magneto-optical (MO) effect allows red- and blue- spectral shift of the Fano profile for right- and left- circular polarizations of the external light, rendering Fano switching sensitive to the light polarization. Specifically, one can reach Fano switching for the right circular polarization while cancelling it for the left circular polarization. Our results point to a novel class of ultrafast Fano switchers tunable by magnetic field for applications in nanophotonics.

[58]  arXiv:1802.06643 [pdf]
Title: Electrically Conductive Diamond Membrane for Electrochemical Separation Processes
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Electrochemically switchable selective membranes play an important role in selective filtration processes such as water desalination, industrial waste treatment and hemodialysis. Currently, membranes for these purposes need to be optimized in terms of electrical conductivity and stability against fouling and corrosion. In this paper, we report the fabrication of boron-doped diamond membrane by template diamond growth on quartz fiber filters. The morphology and quality of the diamond coating are characterized via SEM and Raman spectroscopy. The membrane is heavily boron doped (> 1021 cm-3) with > 3 V potential window in aqueous electrolyte. By applying a membrane potential against the electrolyte, redox active species can be removed via flow-through electrolysis. Compared to planar diamond electrodes, the ~250 times surface enlargement provided by such a membrane ensures an effective removal of target chemicals from the input electrolyte. The high stability of diamond enables the membrane to not only work at high membrane bias but also to be self-cleaning via in situ electrochemical oxidation. Therefore, we believe that the diamond membrane presented in this paper will provide a solution to future selective filtration applications especially in extreme conditions.

[59]  arXiv:1802.06689 [pdf]
Title: The Role of Solvent for Sodium Intercalation into Graphite
Comments: 15 pages, 5 figures
Subjects: Chemical Physics (physics.chem-ph); Materials Science (cond-mat.mtrl-sci)

Na is known to deliver very low energy capacity for sodium intercalation compared to Lithium. In this study, we use quantum mechanics based metadynamics simulations to obtain the free energy landscape for sodium ion intercalation from Dimethyl sulfoxide (DMSO) solvent into graphite. We find that the lowest free energy minima from the metadynamics are associated with sodium solvated by 3 or 4 DMSO. The free energy minima of these states are activated by a free energy of solvation computed to be 0.17 eV, which in turn are the most thermodynamically stable. We observe weak interactions of sodium with graphite sheets during the unbiased and biased molecular dynamics simulations. Our simulations results indicate that solvent plays an important role in stabilizing the sodium intercalation into graphite through shielding of the sodium while modulating the interaction of the solvent with the graphite sheets. In order to facilitate this intercalation, we propose solvents with negatively charged groups and aromatic cores (e.g., cyclic ethers) that could allow a greater rate of anion exchange to increase Na+ mobility.

[60]  arXiv:1802.06690 [pdf, other]
Title: A Laplace Transform Method for Molecular Mass Distribution Calculation from Rheometric Data
Authors: Christian Lang
Journal-ref: Journal of Rheology 61, 947 (2017)
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Physics (physics.comp-ph)

Polydisperse linear polymer melts can be microscopically described by the tube model and fractal reptation dynamics, while on the macroscopic side the generalized Maxwell model is capable of correctly displaying most of the rheological behavior. In this paper, a Laplace transform method is derived and different macroscopic starting points for molecular mass distribution calculation are compared to a classical light scattering evaluation. The underlying assumptions comprise the modern understanding on polymer dynamics in entangled systems but can be stated in a mathematically generalized way. The resulting method is very easy to use due to its mathematical structure and it is capable of calculating multimodal molecular mass distributions of linear polymer melts.

[61]  arXiv:1802.06692 [pdf]
Title: Complexity-weighted doses reduce biological uncertainty in proton radiotherapy planning
Subjects: Medical Physics (physics.med-ph)

Purpose: Variations in proton Relative Biological Effectiveness (RBE) with Linear Energy Transfer (LET) remain one of the largest sources of uncertainty in proton radiotherapy. This work seeks to identify physics-based metrics which can be applied to reduce this biological uncertainty.
Materials and Methods: Three different physical metrics - dose, dose $\times$ LET and a complexity-weighted dose (CWD, Dose $\times$ (1+$\kappa LET_D$) ) were compared with in vitro experimental studies of proton RBE and clinical treatment plans analysed using RBE models. The biological effects of protons in each system were plotted against these metrics to quantify the degree of biological uncertainty introduced by RBE variations in each case.
Results: When the biological effects of protons were plotted against dose alone, significant biological uncertainty was introduced as the LET-dependence of RBE was neglected. Plotting biological effects against dose $\times$ LET significantly over-estimated the impact of LET on cell survival, leading to similar or greater levels of biological uncertainty. CWD, by contrast, significantly reduced biological uncertainties in both experiments and clinical plans. For prostate and medulloblastoma treatment plans, biological uncertainties were reduced from $\pm$ 5% to less than 1%.
Conclusions: While not a replacement for full RBE models, physics-based metrics such as CWD have the potential to significantly reduce the uncertainties in proton planning which result from variations in RBE. These metrics may be used to identify regions in normal tissues which may see unexpectedly high effects due to end-of-range elevations of RBE, or as a tool in optimisation to deliver uniform biological effects.

[62]  arXiv:1802.06695 [pdf, other]
Title: Structural diradical character
Subjects: Computational Physics (physics.comp-ph); Chemical Physics (physics.chem-ph)

A reliable first-principles description of singlet diradical character is essential for predicting nonlinear optical and magnetic properties of molecules. Since diradical and closed-shell electronic structures differ in their distribution of single, double, and triple bonds, modeling electronic diradical character requires accurate bond-length patterns. A generally applicable measure for comparing first-principles bond-length patterns with experimental ones is not available at present. For this purpose, we introduce a new measure for structural (rather than electronic) diradical character. It has the advantage of being easily applicable to both computed and experimental molecular structures for arbitrary systems. Within Kohn-Sham density functional theory, we employ this measure for evaluating the suitability of four popular approximate exchange-correlation functionals with different exact-exchange admixtures (BP86, TPSS, B3LYP, TPSSh) for describing experimentally characterized organometallic and organic structures at the diradical / closed-shell border. The two hybrid functionals TPSSh and B3LYP perform best for diradical bond length patterns, with TPSSh being best for the organometallic reference systems and B3LYP for the organic ones. Still, none of the functionals is suitable for correctly describing relative bond lengths across the range of molecules studied, so that none can be recommended for predictive studies of (potential) diradicals without reservation. This underlines the importance of structural diradical character as a test for the further evaluation and development of electronic structure methods.

[63]  arXiv:1802.06705 [pdf]
Title: Microdosimetry in ion-beam therapy: studying and comparing outcomes from different detectors
Authors: Giulio Magrin
Comments: 23 pages; 7 figures; 2 tables
Subjects: Instrumentation and Detectors (physics.ins-det); Medical Physics (physics.med-ph)

Experimental studies of microdosimetry in therapeutic ion beams have been performed using several detectors. The differences among them lie on the shapes, the site sizes, and the material. Coin-shaped solid-state detectors made of silicon or diamond with thickness varying from 0.3 to 10 microns, as well as proportional counters with spherical and cylindrical sensitive volumes filled with tissue-equivalent gas are the microdosimeters used in therapeutic proton and carbon-ion beams. One goal of microdosimetry in the clinical environment is providing repeatable specification of the radiation quality of the radiation field. A methodology should be developed to provide, independently from the heterogeneous information collected with the different detectors, a detector-independent specification of the radiation quality. Historically the specification of the radiation quality is provided either, in terms of Linear Energy Transfer (LET) or in terms of lineal energy, y. First this study focuses on identifying the correlation between the distributions of LET and the lineal energy spectra as well as the correspondence between their mean values calculated in frequency and in dose. The evaluation is based on the method of LET analysis described by Kellerer making the adaptation to the peculiarities of the therapeutic ion-beam where the pristine irradiation is unidirectional and made of a single type of mono-energetic ions. The second objective of this study is to interpret the spectrum collected by a slab and estimate what the spectrum would be if it was collected by a detector different in shape, material, or size. An example confirms the method starting from the simulated lineal energy spectrum obtained for carbon ions in a slab detector of graphite and converting it to the spectruma that would be obtained in the same radiation field for spherical, cylindrical, and slab detector made of water.

[64]  arXiv:1802.06721 [pdf, ps, other]
Title: Segregation in Religion Networks
Comments: 11 pages, 2 figures
Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI)

Religious beliefs could facilitate human cooperation [1-6], promote civic engagement [7-10], improve life satisfaction [11-13] and even boom economic development [14-16]. On the other side, some aspects of religion may lead to regional violence, intergroup conflict and moral prejudice against atheists [17-23]. Analogous to the separation of races [24], the religious segregation is a major ingredient resulting in increasing alienation, misunderstanding, cultural conflict and even violence among believers of different faiths [18,19,25]. Thus far, quantitative understanding of religious segregation is rare. Here we analyze a directed social network extracted from weibo.com (the largest directed social network in China, similar to twitter.com), which is consisted of 6875 believers in Christianism, Buddhism, Islam and Taoism. This religion network is highly segregative, with only 1.6% of links connecting individuals in different religions. Comparative analysis shows that the extent of segregation for different religions is much higher than that for different races and slightly higher than that for different political parties. The few cross-religion links play a critical role in maintaining network connectivity, being remarkably more important than links with highest betweennesses [26] or bridgenesses [27]. Further content analysis shows that 46.7% of these cross-religion links are probably related to charitable issues. Our findings provide quantitative insights into religious segregation and valuable clues to encourage cross-religion communications.

[65]  arXiv:1802.06722 [pdf, ps, other]
Title: Unified Classical and `Quantum Mechanical' Gravity!
Authors: Partha Ghose
Comments: 4 pages, no figures
Subjects: General Physics (physics.gen-ph)

It is shown that a unified description of classical and `quantum mechanical' gravity in its linearized form is possible.

[66]  arXiv:1802.06728 [pdf, other]
Title: Modulation of kinetic Alfvén waves in an intermediate magnetoplasma
Comments: 7 pages, 3 figures
Subjects: Plasma Physics (physics.plasm-ph)

We study the amplitude modulation of nonlinear kinetic Alfv\'en waves (KAWs) in an intermediate magnetoplasma. Starting from a set of fluid equations coupled to the Maxwell's equations, we derive a coupled set of nonlinear partial differential equations (PDEs) which govern the evolution of KAW envelopes in the plasma. The modulational instability (MI) of such KAW envelopes is then studied by a nonlinear Schr\"odinger (NLS) equation derived from the coupled PDEs. It is shown that the KAWs can evolve into bright and dark envelope solitons, or can undergo damping depending on whether the characteristic ratio $(\alpha)$ of the Alfv\'en to ion-acoustic (IA) speeds remains above or below a critical value. The parameter $\alpha$ is also found to shift the MI domains around the $k_xk_z$ plane, where $k_x~(k_z)$ is the KAW number perpendicular (parallel) to the external magnetic field. The growth rate of MI, as well as the frequency shift and the energy transfer rate, are obtained and analyzed. The results can be useful for understanding the existence and formation of bright and dark envelope solitons, or damping of KAW envelopes in space plasmas, e.g., interplanetary space, solar winds etc.

[67]  arXiv:1802.06729 [pdf, ps, other]
Title: Analytical model of a 3D beam dynamics in a wakefield device
Comments: 5 pages, 3 figures
Subjects: Accelerator Physics (physics.acc-ph)

In this paper we suggest an analytical model and derive a simple formula for the beam dynamics in a wakefield structure of arbitrary cross-section. Result could be applied to the estimation of an upper limit of the projected beam size in devices such as the dechirper and the wakefield striker. Suggested formalism could be applied to the case when slices of the beam are distributed along an arbitrary 3D line.

[68]  arXiv:1802.06737 [pdf, other]
Title: Measurement of optical constants of TiN and TiN/Ti/TiN multilayer films for microwave kinetic inductance photon-number-resolving detectors
Subjects: Optics (physics.optics); Applied Physics (physics.app-ph)

We deposit thin titanium-nitride (TiN) and TiN/Ti/TiN multilayer films on sapphire substrates and measure the reflectance and transmittance in the wavelength range from 400 nm to 2000 nm using a spectrophotometer. The optical constants (complex refractive indices), including the refractive index n and the extinction coefficient k, have been derived. With the extracted refractive indices, we propose an optical stack structure using low-loss amorphous Si (a-Si) anti-reflective coating and a backside aluminum (Al) reflecting mirror, which can in theory achieve 100% photon absorption at 1550 nm. The proposed optical design shows great promise in enhancing the optical efficiency of TiN-based microwave kinetic inductance photon-number-resolving detectors.

[69]  arXiv:1802.06738 [pdf, other]
Title: Exploration of Reduced Scaling Formulation of Equation of Motion Coupled-Cluster Singles and Doubles Based on State-Averaged Pair Natural Orbitals
Comments: 28 pages, 6 figures
Subjects: Chemical Physics (physics.chem-ph)

A reduced-complexity variant of equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) method is formulated in terms of state-averaged excited state pair natural orbitals (PNO) designed to describe manifolds of excited states. State-averaged excited state PNOs for the {\em target} manifold are determined by averaging CIS(D) pair densities over the computational manifold. To assess the performance of PNO-EOM-CCSD approach on extended systems the new massively parallel canonical EOM-CCSD program has been developed in the Massively Parallel Quantum Chemistry program that allows treatment of systems with 50+ atoms using realistic basis sets with 1000+ functions. The use of state-averaged PNOs offers several potential advantages relative to the recently proposed state-specific PNOs: our approach is robust with respect to root flipping and state degeneracies, it is more economical when computing large manifolds of states, and it simplifies evaluation of transition-specific observables such as dipole moments. With the PNO truncation threshold of $10^{-7}$, the errors in excitation energies are on average below 0.02 eV for the first six singlet states of 28 organic molecules included in the standard test set of Thiel and co-workers (J. Chem. Phys. 2008, 128, 134110) with 50-70 state-averaged PNOs per pair.

[70]  arXiv:1802.06743 [pdf, other]
Title: Spectral/hp element methods: recent developments, applications, and perspectives
Subjects: Fluid Dynamics (physics.flu-dyn); Computational Physics (physics.comp-ph)

The spectral/hp element method combines the geometric flexibility of the classical h-type finite element technique with the desirable numerical properties of spectral methods, employing high-degree piecewise polynomial basis functions on coarse finite element-type meshes. The spatial approximation is based upon orthogonal polynomials, such as Legendre or Chebychev polynomials, modified to accommodate C0-continuous expansions. Computationally and theoretically, by increasing the polynomial order p, high-precision solutions and fast convergence can be obtained and, in particular, under certain regularity assumptions an exponential reduction in approximation error between numerical and exact solutions can be achieved. This method has now been applied in many simulation studies of both fundamental and practical engineering flows. This paper briefly describes the formulation of the spectral/hp element method and provides an overview of its application to computational fluid dynamics. In particular, it focuses on the use the spectral/hp element method in transitional flows and ocean engineering. Finally, some of the major challenges to be overcome in order to use the spectral/hp element method in more complex science and engineering applications are discussed.

[71]  arXiv:1802.06745 [pdf, ps, other]
Title: Environmental feedback drives cooperation in spatial social dilemmas
Comments: 7 two-column pages, 4 figures, accepted for publication in EPL
Subjects: Physics and Society (physics.soc-ph); Computer Science and Game Theory (cs.GT); Populations and Evolution (q-bio.PE)

Exploiting others is beneficial individually but it could also be detrimental globally. The reverse is also true: a higher cooperation level may change the environment in a way that is beneficial for all competitors. To explore the possible consequence of this feedback we consider a coevolutionary model where the local cooperation level determines the payoff values of the applied prisoner's dilemma game. We observe that the coevolutionary rule provides a significantly higher cooperation level comparing to the traditional setup independently of the topology of the applied interaction graph. Interestingly, this cooperation supporting mechanism offers lonely defectors a high surviving chance for a long period hence the relaxation to the final cooperating state happens logarithmically slow. As a consequence, the extension of the traditional evolutionary game by considering interactions with the environment provides a good opportunity for cooperators, but their reward may arrive with some delay.

Cross-lists for Tue, 20 Feb 18

[72]  arXiv:1802.05719 (cross-list from quant-ph) [pdf, other]
Title: Generic emergence of objectivity of observables in infinite dimensions
Comments: 15 pages, 3 figures
Subjects: Quantum Physics (quant-ph); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph); History and Philosophy of Physics (physics.hist-ph)

Quantum Darwinism posits that information becomes objective whenever multiple observers indirectly probe a quantum system by each measuring a fraction of the environment. It was recently shown that objectivity of observables emerges generically from the mathematical structure of quantum mechanics, whenever the system of interest has finite dimensions and the number of environment fragments is large [Brand\~ao et. al. (2015), Nat. Commun. 6, 7908]. Despite the importance of this result, it necessarily excludes many practical systems of interest that live in infinite dimensions, including harmonic oscillators. Extending the study of Quantum Darwinism to infinite dimensions is a nontrivial task: we tackle it here by introducing a modified diamond norm, suitable to quantify the distinguishability of channels in infinite dimensions. We prove two theorems that bound the emergence of objectivity, first for finite energy systems, and then for systems that can only be prepared in states with an exponential energy cut-off. We show that the latter class of states includes any bounded-energy subset of single-mode Gaussian states.

[73]  arXiv:1802.06090 (cross-list from q-bio.BM) [pdf]
Title: Unveiled electric profiles within hydrogen bonds suggest DNA base pairs with similar bond strengths
Comments: Full version is available on: this http URL
Journal-ref: PLoS ONE 12(10): e0185638 (2017)
Subjects: Biomolecules (q-bio.BM); Biological Physics (physics.bio-ph)

Electrical forces are the background of all the interactions occurring in biochemical systems. From here and by using a combination of ab-initio and ad-hoc models, we introduce the first description of electric field profiles with intrabond resolution to support a characterization of single bond forces attending to its electrical origin. This fundamental issue has eluded a physical description so far. Our method is applied to describe hydrogen bonds (HB) in DNA base pairs. Numerical results reveal that base pairs in DNA could be equivalent considering HB strength contributions, which challenges previous interpretations of thermodynamic properties of DNA based on the assumption that Adenine/Thymine pairs are weaker than Guanine/Cytosine pairs due to the sole difference in the number of HB. Thus, our methodology provides solid foundations to support the development of extended models intended to go deeper into the molecular mechanisms of DNA functioning.

[74]  arXiv:1802.06100 (cross-list from stat.AP) [pdf, other]
Title: Extreme Value Analysis of Solar Flare Events
Comments: 17 pages, 5 figures
Subjects: Applications (stat.AP); Solar and Stellar Astrophysics (astro-ph.SR); Data Analysis, Statistics and Probability (physics.data-an); Space Physics (physics.space-ph)

Space weather events such as solar flares can be harmful for life and infrastructure on earth or in near-earth orbit. In this paper we employ extreme value theory (EVT) to model extreme solar flare events; EVT offers the appropriate tools for the study and estimation of probabilities for extrapolation to ranges outside of those that have already been observed. In the past such phenomena have been modelled as following a power law which may gives poor estimates of such events due to overestimation. The data used in the study were X-ray fluxes from NOAA/GOES and the expected return levels for Carrington or Halloween like events were calculated with the outcome that the existing data predict similar events happening in 110 and 38 years respectively.

[75]  arXiv:1802.06110 (cross-list from quant-ph) [pdf]
Title: Light, the universe, and everything -- 12 Herculean tasks for quantum cowboys and black diamond skiers
Comments: A review of the leading topics in quantum optics and related areas. Accepted for publication in J. Modern Optics (42 figures, 74 pages)
Subjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other); Optics (physics.optics)

The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mindboggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January, 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world's leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited - such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial, and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centers in diamond? (8) What is the future of quantum coherence, squeezing, and entanglement for enhanced superresolution and sensing? (9) How can we solve (some of) humanity's biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics?

[76]  arXiv:1802.06138 (cross-list from cs.SI) [pdf, other]
Title: Discriminative Modeling of Social Influence for Prediction and Explanation in Event Cascades
Subjects: Social and Information Networks (cs.SI); Learning (cs.LG); Physics and Society (physics.soc-ph)

The global dynamics of event cascades are often governed by the local dynamics of peer influence. However, detecting social influence from observational data is challenging, due to confounds like homophily and practical issues like missing data. In this work, we propose a novel discriminative method to detect influence from observational data. The core of the approach is to train a ranking algorithm to predict the source of the next event in a cascade, and compare its out-of-sample accuracy against a competitive baseline which lacks access to features corresponding to social influence. Using synthetically generated data, we provide empirical evidence that this method correctly identifies influence in the presence of confounds, and is robust to both missing data and misspecification --- unlike popular alternatives. We also apply the method to two real-world datasets: (1) cascades of co-sponsorship of legislation in the U.S. House of Representatives, on a social network of shared campaign donors; (2) rumors about the Higgs boson discovery, on a follower network of $10^5$ Twitter accounts. Our model identifies the role of peer influence in these scenarios, and uses it to make more accurate predictions about the future trajectory of cascades.

[77]  arXiv:1802.06160 (cross-list from cond-mat.supr-con) [pdf]
Title: Effect of $α$-particle irradiation on a NdFeAs(O,F) thin film
Comments: 12 pages, 9 figures
Journal-ref: Supercond. Sci. Technol. 31, 034002 (2018)
Subjects: Superconductivity (cond-mat.supr-con); Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

The effect of $\alpha$-particle irradiation on a NdFeAs(O,F) thin film has been investigated to determine how the introduction of defects affects basic superconducting properties, including the critical temperature $T_c$ and the upper critical field $H_{c2}$, and properties more of interest for applications, like the critical current density $J_c$ and the related pinning landscape. The irradiation-induced suppression of the film $T_c$ is significantly smaller than on a similarly damaged single crystal. Moreover $H_{c2}$ behaves differently, depending on the field orientation: for H//c the $H_{c2}$ slope monotonically increases with increasing disorder, whereas for H//ab it remains constant at low dose and it increases only when the sample is highly disordered. This suggests that a much higher damage level is necessary to drive the NdFeAs(O,F) thin film into the dirty limit. Despite the increase in the low temperature $H_{c2}$, the effects on the $J_c$(H//c) performances are moderate in the measured temperature and field ranges, with a shifting of the pinning force maximum from 4.5 T to 6 T after an irradiation of $2\times10^{15} cm^{-2}$. On the contrary, $J_c$(H//ab) is always suppressed. The analysis demonstrates that irradiation does introduce point defects acting as pinning centres proportionally to the irradiation fluence but also suppresses the effectiveness of c-axis correlated pinning present in the pristine sample. We estimate that significant performance improvements may be possible at high field or at temperatures below 10 K. The suppression of the $J_c$(H//ab) performance is not related to a decrease of the $J_c$ anisotropy as found in other superconductors. Instead it is due to the presence of point defects that decrease the efficiency of the ab-plane intrinsic pinning typical of materials with a layered structure.

[78]  arXiv:1802.06219 (cross-list from cs.SI) [pdf]
Title: Network Centrality Analysis of Tehran Urban and Suburban Railway System
Comments: 8 pages, 3 figures and 1 table
Subjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)

Nowadays, Tehran Urban and Suburban Railway System (TUSRS) is going to be completed by eight lines and 149 stations. This complex transportation system contains 168 links between each station pairs and 20 cross-section and Y-branch stations among all eight lines. In this study, we considered TUSRS as a complex network and undertook several analyzes based on graph theory. Examining e.g. centrality measures, we identified central stations within TUSRS. This analysis could be useful for redistributing strategy of the overcrowded stations and improving the organization of maintaining system. These findings are also promising for better designing the systems of tomorrow in other metropolitan areas in Iran.

[79]  arXiv:1802.06230 (cross-list from nlin.PS) [pdf, ps, other]
Title: Dark-bright soliton pairs: bifurcations and collisions
Comments: 9 pages, 6 figures
Subjects: Pattern Formation and Solitons (nlin.PS); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)

The statics, stability and dynamical properties of dark-bright soliton pairs are investigated motivated by applications in a homogeneous system of two-component repulsively interacting Bose-Einstein condensate. One of the intra-species interaction coefficients is used as the relevant parameter controlling the deviation from the integrable Manakov limit. Two different families of stationary states are identified consisting of dark-bright solitons that are either anti-symmetric (out-of-phase) or asymmetric (mass imbalanced) with respect to their bright soliton. Both of the above dark-bright configurations coexist at the integrable limit of equal intra- and inter-species repulsions and are degenerate in that limit. However, they are found to bifurcate from it in a transcritical bifurcation. The latter interchanges the stability properties of the bound dark-bright pairs rendering the anti-symmetric states unstable and the asymmetric ones stable past the associated critical point (and vice versa before it). Finally, on the dynamical side, it is found that large kinetic energies and thus rapid soliton collisions are essentially unaffected by the intra-species variation, while cases involving near equilibrium states or breathing dynamics are significantly modified under such a variation.

[80]  arXiv:1802.06265 (cross-list from cs.SI) [pdf, other]
Title: Statistical Link Label Modeling for Sign Prediction: Smoothing Sparsity by Joining Local and Global Information
Subjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)

One of the major issues in signed networks is to use network structure to predict the missing sign of an edge. In this paper, we introduce a novel probabilistic approach for the sign prediction problem. The main characteristic of the proposed models is their ability to adapt to the sparsity level of an input network. The sparsity of networks is one of the major reasons for the poor performance of many link prediction algorithms, in general, and sign prediction algorithms, in particular. Building a model that has an ability to adapt to the sparsity of the data has not yet been considered in the previous related works. We suggest that there exists a dilemma between local and global structures and attempt to build sparsity adaptive models by resolving this dilemma. To this end, we propose probabilistic prediction models based on local and global structures and integrate them based on the concept of smoothing. The model relies more on the global structures when the sparsity increases, whereas it gives more weights to the information obtained from local structures for low levels of the sparsity. The proposed model is assessed on three real-world signed networks, and the experiments reveal its consistent superiority over the state of the art methods. As compared to the previous methods, the proposed model not only better handles the sparsity problem, but also has lower computational complexity and can be updated using real-time data streams.

[81]  arXiv:1802.06287 (cross-list from stat.ML) [pdf, other]
Title: Unsupervised vehicle recognition using incremental reseeding of acoustic signatures
Subjects: Machine Learning (stat.ML); Learning (cs.LG); Data Analysis, Statistics and Probability (physics.data-an)

Vehicle recognition and classification have broad applications, ranging from traffic flow management to military target identification. We demonstrate an unsupervised method for automated identification of moving vehicles from roadside audio sensors. Using a short-time Fourier transform to decompose audio signals, we treat the frequency signature in each time window as an individual data point. We then use a spectral embedding for dimensionality reduction. Based on the leading eigenvectors, we relate the performance of an incremental reseeding algorithm to that of spectral clustering. We find that incremental reseeding accurately identifies individual vehicles using their acoustic signatures.

[82]  arXiv:1802.06374 (cross-list from quant-ph) [pdf]
Title: Quantum metamaterials: entanglement of spin and orbital angular momentum of a single photon
Subjects: Quantum Physics (quant-ph); Optics (physics.optics)

Metamaterials have been a major research area for more than two decades now, involving artificial structures with predesigned electromagnetic properties constructed from deep subwavelength building blocks. They have been used to demonstrate a wealth of fascinating phenomena ranging from negative refractive index and epsilon-near-zero to cloaking, emulations of general relativity effects, and super-resolution imaging, to name a few. In the past few years, metamaterials have been suggested as a new platform for quantum optics, and several pioneering experiments have already been carried out with single photons. Here, we employ a dielectric metasurface to generate entanglement between spin and orbital angular momentum of single photons. We demonstrate experimentally the generation of the four Bell states by utilizing the geometric phase arising from the photonic spin-orbit interaction. These are the first experiments with entangled states with metasurfaces, and as such they are paving the way to the new area of quantum metamaterials.

[83]  arXiv:1802.06422 (cross-list from math.DS) [pdf, ps, other]
Title: Stochastic stability of invariant measures: The 2D Euler equation
Comments: 12 pages Latex
Subjects: Dynamical Systems (math.DS); Fluid Dynamics (physics.flu-dyn)

In finite-dimensional dynamical systems, stochastic stability provides the selection of physical relevant measures from the myriad invariant measures of conservative systems. That this might also apply to infinite-dimensional systems is the inspiration for this work. As an example the 2D Euler equation is studied. Among other results this study suggests that the coherent structures observed in 2D hydrodynamics are associated to configurations that maximize stochastically stable measures uniquely determined by the boundary conditions in mode space.

[84]  arXiv:1802.06437 (cross-list from cs.SI) [pdf, other]
Title: What We Read, What We Search: Media Attention and Public Attention Among 193 Countries
Comments: Will be presented in the Web Conference 2018 (WWW2018)
Subjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)

We investigate the alignment of international attention of news media organizations within 193 countries with the expressed international interests of the public within those same countries from March 7, 2016 to April 14, 2017. We collect fourteen months of longitudinal data of online news from Unfiltered News and web search volume data from Google Trends and build a multiplex network of media attention and public attention in order to study its structural and dynamic properties. Structurally, the media attention and the public attention are both similar and different depending on the resolution of the analysis. For example, we find that 63.2% of the country-specific media and the public pay attention to different countries, but local attention flow patterns, which are measured by network motifs, are very similar. We also show that there are strong regional similarities with both media and public attention that is only disrupted by significantly major worldwide incidents (e.g., Brexit). Using Granger causality, we show that there are a substantial number of countries where media attention and public attention are dissimilar by topical interest. Our findings show that the media and public attention toward specific countries are often at odds, indicating that the public within these countries may be ignoring their country-specific news outlets and seeking other online sources to address their media needs and desires.

[85]  arXiv:1802.06469 (cross-list from cond-mat.soft) [pdf, ps, other]
Title: Active fluids at circular boundaries: Swim pressure and anomalous droplet ripening
Comments: 15 pages, 7 figures
Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph); Chemical Physics (physics.chem-ph)

We investigate the swim pressure exerted by non-chiral and chiral active particles on convex or concave circular boundaries. Active particles are modeled as non-interacting and non-aligning self-propelled Brownian particles. The convex and concave circular boundaries are used as models representing a fixed inclusion immersed in an active bath and a cavity (or container) enclosing the active particles, respectively. We first present a detailed analysis of the role of convex versus concave boundary curvature and of the chirality of active particles on their spatial distribution, chirality-induced currents, and the swim pressure they exert on the bounding surfaces. The results will then be used to predict the mechanical equilibria of suspended fluid enclosures (generically referred to as 'droplets') in a bulk with active particles being present either inside the bulk fluid or within the suspended droplets. We show that, while droplets containing active particles and suspended in a normal bulk behave in accordance with standard capillary paradigms, those containing a normal fluid exhibit anomalous behaviors when suspended in an active bulk. In the latter case, the excess swim pressure results in non-monotonic dependence of the inside droplet pressure on the droplet radius. As a result, we find a regime of anomalous capillarity for a single droplet, where the inside droplet pressure increases upon increasing the droplet size. In the case of two interconnected droplets, we show that mechanical equilibrium can occur also when they have different sizes. We further identify a regime of anomalous ripening, where two unequal-sized droplets can reach a final state of equal sizes upon interconnection, in stark contrast with the standard Ostwald ripening phenomenon, implying shrinkage of the smaller droplet in favor of the larger one.

[86]  arXiv:1802.06505 (cross-list from cs.SI) [pdf, other]
Title: What Do Your Friends Think? Efficient Polling Methods for Networks Using Friendship Paradox
Subjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)

This paper deals with randomized polling of a social network. In the case of forecasting the outcome of an election between two candidates A and B, classical intent polling asks randomly sampled individuals: who will you vote for? Expectation polling asks: who do you think will win? In this paper, we propose a novel neighborhood expectation polling (NEP) strategy that asks randomly sampled individuals: what is your estimate of the fraction of votes for A? Therefore, in NEP, sampled individuals will naturally look at their neighbors (defined by the underlying social network graph) when answering this question. Hence, the mean squared error (MSE) of NEP methods rely on selecting the optimal set of samples from the network. To this end, we propose three NEP algorithms for the following cases: (i) the social network graph is not known but, random walks (sequential exploration) can be performed on the graph (ii) the social network graph is unknown. For case (i) and (ii), two algorithms based on a graph theoretic consequence called friendship paradox are proposed. Theoretical results on the dependence of the MSE of the algorithms on the properties of the network are established. Numerical results on real and synthetic data sets are provided to illustrate the performance of the algorithms.

[87]  arXiv:1802.06534 (cross-list from cond-mat.soft) [pdf, ps, other]
Title: A Simple and Effective Solution to the Constrained QM/MM Simulations
Subjects: Soft Condensed Matter (cond-mat.soft); Chemical Physics (physics.chem-ph)

It is a promising extension of the quantum mechanical/molecular mechanical (QM/MM) approach to incorporate the solvent molecules surrounding the QM solute into the QM region to ensure the adequate description of the electronic polarization of the solute. However, the solvent molecules in the QM region inevitably diffuse into the MM bulk during the QM/MM simulation. In this article we developed a simple and efficient method, referred to as boundary constraint with correction (BCC), to prevent the diffusion of the solvent water molecules by means of a constraint po- tential. The point of the BCC method is to compensate the error in a statistical property due to the bias potential by adding a correction term obtained through a set of QM/MM simulations. The BCC method is designed so that the effect of the bias potential completely vanishes when the QM solvent is identical with the MM solvent. Furthermore, the desirable conditions, that is, the continuities of energy and force and the conservations of energy and momentum, are fulfilled in principle. We applied the QM/MM-BCC method to a hydronium ion in aqueous solution to construct the radial distribution function(RDF) of the solvent around the solute. It was demonstrated that the correction term fairly compensated the error and led the RDF in good agreement with the result given by an ab initio molecular dynamics simulation.

[88]  arXiv:1802.06569 (cross-list from quant-ph) [pdf, other]
Title: Non-Hermiticity and conservation of orthogonal relation in dielectric microcavity
Comments: 11 pages, 5 figures
Subjects: Quantum Physics (quant-ph); Optics (physics.optics)

Non-Hermitian properties of open quantum systems and their applications have attracted much attention in recent years. While most of the studies focus on the characteristic nature of non-Hermitian systems, one important point has been overlooked: A non-Hermitian system can be a subsystem of a Hermitian system as one can clearly see in Feshbach projective operator (FPO) formalism. In this case, the orthogonality of the eigenvectors of the total (Hermitian) system must be sustained, despite the eigenvectors of the subsystem (non-Hermitian) satisfy the bi-orthogonal condition. Therefore, one can predict that there must exist some remarkable processes that relate the non-Hermitian subsystem and the rest part, and ultimately preserve the Hermiticity of the total system. In this paper, we study such processes in open elliptical microcavities. The inner part of the cavity is a non-Hermitian system, and the outer part is the coupled bath in FPO formalism. We investigate the correlation between the inner- and the outer-part behaviors associated with the avoided resonance crossings (ARCs), and analyze the results in terms of the Lamb shift. The ARC structures we examined depend on a trade-off between the relative difference of self-energies (simply known as Lamb shifts in atomic physics) and collective Lamb shifts. While the collective Lamb shift is maximized in the region of the center of ARC, but the relative difference of self-energies is minimized, and this naturally induce a crossing of imaginary part of eigenvalues. These results come from the conservation of the orthogonality in the total Hermitian quantum system.

[89]  arXiv:1802.06580 (cross-list from cond-mat.dis-nn) [pdf, other]
Title: Oscillation death induced by time-varying network
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Pattern Formation and Solitons (nlin.PS); Physics and Society (physics.soc-ph); Neurons and Cognition (q-bio.NC)

The synchronous dynamics of an array of excitable oscillators, coupled via a generic graph, is studied. Non homogeneous perturbations can grow and destroy synchrony, via a self-consistent instability which is solely instigated by the intrinsic network dynamics. By acting on the characteristic time-scale of the network modulation, one can make the examined system to behave as its (partially) averaged analog. This result if formally obtained by proving an extended version of the averaging theorem, which allows for partial averages to be carried out. Oscillation death are reported to follow the onset of the network driven instability.

[90]  arXiv:1802.06693 (cross-list from cond-mat.quant-gas) [pdf, ps, other]
Title: Quench Dynamics of Finite Bosonic Ensembles in Optical Lattices with Spatially Modulated Interactions
Comments: 14 pages, 7 figures
Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)

The nonequilibrium quantum dynamics of few boson ensembles which experience a spatially modulated interaction strength and are confined in finite optical lattices is investigated. Performing quenches either on the wavevector or the phase of the interaction profile an enhanced imbalance of the interatomic repulsion between distinct spatial regions of the lattice is induced. Following both quench protocols triggers various tunneling channels and a rich excitation dynamics consisting of a breathing and a cradle mode. All modes are shown to be amplified for increasing inhomogeneity amplitude of the interaction strength. Especially the phase quench induces a directional transport enabling us to discern energetically, otherwise, degenerate tunneling pathways. Moreover, a periodic population transfer between distinct momenta for quenches of increasing wavevector is observed, while a directed occupation of higher momenta can be achieved following a phase quench. Finally, during the evolution regions of partial coherence are revealed between the predominantly occupied wells.

[91]  arXiv:1802.06727 (cross-list from astro-ph.IM) [pdf, other]
Title: Thorough experimental testing of Multimode interference couplers and expected nulls thereof; for exoplanet detection
Comments: Only a first draft. Will upload later versions as we go
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); Optics (physics.optics)

In exoplanet interferometry a null of 40~dB is a large step in achieving the ability to directly image an Earth-like planet that is in the habitable zone around a star like our own. Based on the standard procedure at the Australian National University we have created a nulling interferometer that has achieved a 25~dB null in the astronomical L~band under laboratory conditions. The device has been constructed on a 2-dimensional platform of chalcogenide glass: a three layered structure of $Ge_{11.5}As_{24}S_{64.5}$ undercladding, 2~\si{\um} of $Ge_{11.5}As_{24}Se_{64.5}$ core and an angled deposition of $Ge_{11.5}As_{24}S_{64.5}$ as a complete overcladding. Matching simulation from Rsoft and individual results of the MMIs the expected null should produce a null of 40~dB over a bandwidth of 400~nm but due to limitations in mask design and light contamination only a 25~dB extinction can be reliably achieved.

[92]  arXiv:1802.06732 (cross-list from math.OC) [pdf, other]
Title: Congestion analysis of unsignalized intersections: The impact of impatience and Markov platooning
Comments: An earlier, related paper which also contains some of the results (in more detail) published in the present paper, appeared in the proceedings of the 8th International Conference on Communication Systems and Networks (COMSNETS), 5-10 Jan. 2016. This conference paper can also be found on arXiv and in IEEE Xplore: this http URL
Subjects: Optimization and Control (math.OC); Probability (math.PR); Physics and Society (physics.soc-ph)

This paper considers an unsignalized intersection used by two traffic streams. A stream of cars is using a primary road, and has priority over the other stream. Cars belonging to the latter stream cross the primary road if the gaps between two subsequent cars on the primary road are larger than their critical headways. A question that naturally arises relates to the capacity of the secondary road: given the arrival pattern of cars on the primary road, what is the maximum arrival rate of low-priority cars that can be sustained? This paper addresses this issue by considering a compact model that sheds light on the dynamics of the considered unsignalized intersection. The model, which is of a queueing-theoretic nature, reveals interesting insights into the impact of the user behavior on stability.
The contributions of this paper are threefold. First, we obtain new results for the aforementioned model that includes driver impatience. Secondly, we reveal some surprising aspects that have remained unobserved in the existing literature so far, many of which are caused by the fact that the capacity of the minor road cannot be expressed in terms of the \emph{mean} gap size; instead more detailed characteristics of the critical headway distribution play a crucial role. The third contribution is the introduction of a new form of bunching on the main road, called Markov platooning. The tractability of this model allows us to study the impact of various platoon formations on the main road on the capacity of the minor road.

Replacements for Tue, 20 Feb 18

[93]  arXiv:1403.6562 (replaced) [pdf, ps, other]
Title: Do the Navier-Stokes equations embody all physics in a flow of Newtonian fluids?
Comments: A conference paper of American Physical Society 67th Annual DFD Meeting
Subjects: Fluid Dynamics (physics.flu-dyn)
[94]  arXiv:1503.05577 (replaced) [pdf, ps, other]
Title: On the Equivalence Principle and Electrodynamics of Moving Bodies
Comments: 18 pages
Journal-ref: EPL (Europhysics Letters), Volume 120, Number 4, 2018
Subjects: General Physics (physics.gen-ph)
[95]  arXiv:1511.01238 (replaced) [pdf]
Title: Fast and slow thinking -- of networks: The complementary 'elite' and 'wisdom of crowds' of amino acid, neuronal and social networks
Authors: Peter Csermely
Comments: This a preliminary version of the paper below, please find its illustrative videos here: this http URL
Journal-ref: BioEssays 40, 1700150 (2018)
Subjects: Molecular Networks (q-bio.MN); Disordered Systems and Neural Networks (cond-mat.dis-nn); Social and Information Networks (cs.SI); Adaptation and Self-Organizing Systems (nlin.AO); Biological Physics (physics.bio-ph)
[96]  arXiv:1607.01380 (replaced) [pdf, ps, other]
Title: Hydrodynamic and Magnetohydrodynamic Extensions on the Parker's Supersonic Stellar Wind Model
Authors: B. K. Shivamoggi
Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR)
[97]  arXiv:1609.09331 (replaced) [pdf, other]
Title: Consistency of detrended fluctuation analysis
Authors: Ola Løvsletten
Journal-ref: Phys. Rev. E 96, 012141 (2017)
Subjects: Statistics Theory (math.ST); Data Analysis, Statistics and Probability (physics.data-an)
[98]  arXiv:1611.03880 (replaced) [pdf, other]
Title: Statistical properties for directional alignment and chasing of players in football games
Comments: 16pages, 12 figures, 3 tables
Journal-ref: Europhysics Letters, Vol. 116, 68001 (2016)
Subjects: Physics and Society (physics.soc-ph)
[99]  arXiv:1612.09180 (replaced) [pdf, other]
Title: A comparison of Hake's g and Cohen's d for analyzing gains on concept inventories
Subjects: Physics Education (physics.ed-ph)
[100]  arXiv:1703.02893 (replaced) [pdf, ps, other]
Title: Analytic Expressions for Exponentials of Specific Hamiltonian Matrices
Authors: C. Baumgarten
Comments: Some typos corrected
Subjects: General Physics (physics.gen-ph)
[101]  arXiv:1703.09430 (replaced) [pdf, other]
Title: Polling bias and undecided voter allocations: US Presidential elections, 2004 - 2016
Comments: 31 pages, 9 figures, 4 tables
Subjects: Applications (stat.AP); Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)
[102]  arXiv:1703.10767 (replaced) [pdf, other]
Title: Weight of fitness deviation governs strict physical chaos in replicator dynamics
Comments: 13 pages, 3 figures; accepted in Chaos
Subjects: Chaotic Dynamics (nlin.CD); Biological Physics (physics.bio-ph)
[103]  arXiv:1705.09136 (replaced) [pdf, other]
Title: Coherent single-atom superradiance
Comments: 18 pages, 9 figures
Journal-ref: Science 359, 662-666 (2018)
Subjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph); Optics (physics.optics)
[104]  arXiv:1705.09869 (replaced) [pdf, other]
Title: Dimensionality reduction for acoustic vehicle classification with spectral embedding
Comments: Proceedings of the 15th IEEE International Conference on Networking, Sensing and Control (2018)
Subjects: Machine Learning (stat.ML); Learning (cs.LG); Data Analysis, Statistics and Probability (physics.data-an)
[105]  arXiv:1706.10287 (replaced) [pdf, other]
Title: Generation of turbulence through frontogenesis in sheared stratified flows
Comments: 19 pages, 15 figures, several simulations added in this new version
Subjects: Fluid Dynamics (physics.flu-dyn); Atmospheric and Oceanic Physics (physics.ao-ph)
[106]  arXiv:1707.07160 (replaced) [pdf, other]
Title: Majorana states for subluminal structured photons
Authors: Fabrizio Tamburini (1,2), Bo Thidé (3), Ignazio Licata (4,5,6), Frédéric Bouchard (7), Ebrahim Karimi (7,8) ((1) Zentrum für Kunst und Medientechnologie, Karlsruhe, Germany, (2) MSC-BW, Stuttgart, Stuttgart, Germany, (3) Swedish Institute of Space Physics, Ångström Laboratory, Uppsala, Sweden, (4) Institute for Scientific Methodology (ISEM) Palermo Italy, (5) School of Advanced International Studies on Theoretical and Nonlinear Methodologies of Physics, Bari, Italy, (6) International Institute for Applicable Mathematics and Information Sciences (IIAMIS), B.M. Birla Science Centre, Adarsh Nagar, Hyderabad, India, (7) Department of Physics, University of Ottawa, Ottawa, Ontario, Canada, (8) Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran)
Comments: 6 pages, 1 figure
Subjects: Optics (physics.optics)
[107]  arXiv:1707.09478 (replaced) [pdf, other]
Title: Global Sensitivity Analysis and Estimation of Model Error, Toward Uncertainty Quantification in Scramjet Computations
Comments: Preprint 29 pages, 10 figures (26 small figures); v1 submitted to the AIAA Journal on May 3, 2017; v2 submitted on September 17, 2017. v2 changes: (a) addition of flowcharts in Figures 4 and 5 to summarize the tools used; (b) edits to clarify and reorganize certain parts; v3 submitted on February 7, 2018. v3 changes: (a) title; (b) minor edits
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn)
[108]  arXiv:1708.00110 (replaced) [pdf, other]
Title: Naturally occurring $^{32}$Si and low-background silicon dark matter detectors
Comments: 16 pages, 4 figures
Journal-ref: Astroparticle Physics 99 (2018) 9-20
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)
[109]  arXiv:1708.09444 (replaced) [pdf, other]
Title: A domain-decomposition method to implement electrostatic free boundary conditions in the radial direction for electric discharges
Comments: 21 pages, 4 figures, a movie and a sample code in python. A new Appendix has been added
Subjects: Plasma Physics (physics.plasm-ph); Computational Physics (physics.comp-ph)
[110]  arXiv:1710.02784 (replaced) [pdf, other]
Title: An Aerodynamic Analysis of Recent FIFA World Cup Balls
Comments: 18 pages, 11 figures, 2 tables
Subjects: Popular Physics (physics.pop-ph)
[111]  arXiv:1710.04538 (replaced) [pdf, ps, other]
Title: Causality Testing: A Data Compression Framework
Comments: 6 pages, 4 figures in main article and 7 pages, 8 figures in supplemental material
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Biological Physics (physics.bio-ph); Neurons and Cognition (q-bio.NC)
[112]  arXiv:1710.07311 (replaced) [pdf, other]
Title: Limitations in Predicting the Space Radiation Health Risk for Exploration Astronauts
Comments: Accepted for publication by Nature Microgravity (2018)
Subjects: Medical Physics (physics.med-ph); Biological Physics (physics.bio-ph); Space Physics (physics.space-ph)
[113]  arXiv:1710.08790 (replaced) [pdf, other]
Title: Molecular Origin of Contact Line Friction in Dynamic Wetting
Authors: Petter Johansson (1), Berk Hess (1) ((1) KTH Royal Institute of Technology, Stockholm, Sweden)
Subjects: Fluid Dynamics (physics.flu-dyn)
[114]  arXiv:1711.04028 (replaced) [pdf, other]
Title: The vector field of a rolling rigid body
Comments: Added semi-symplectic reduction. Will be published as e-print only. 8 pages
Subjects: Mathematical Physics (math-ph); Dynamical Systems (math.DS); Classical Physics (physics.class-ph)
[115]  arXiv:1711.06002 (replaced) [pdf, other]
Title: Bayesian uncertainty quantification in linear models for diffusion MRI
Comments: Added results from a group analysis and a comparison with residual bootstrap
Subjects: Applications (stat.AP); Data Analysis, Statistics and Probability (physics.data-an); Medical Physics (physics.med-ph)
[116]  arXiv:1712.01912 (replaced) [pdf, ps, other]
Title: Quantum dynamics of the intramolecular vibrational energy redistribution in OCS: From localization to quasi-thermalization
Comments: 18 pages, 11 figures
Subjects: Quantum Physics (quant-ph); Chemical Physics (physics.chem-ph)
[117]  arXiv:1712.03116 (replaced) [pdf, other]
Title: Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser
Comments: 4 figures, 10 pages
Journal-ref: Applied Physics Letters 112(6) (2018) 061109
Subjects: Optics (physics.optics)
[118]  arXiv:1712.03526 (replaced) [pdf, other]
Title: Improved performance of semiconductor laser tracking frequency gauge
Comments: 8 pages, 4 figures. To appear in JINST. (This version with new figures 3 and 4 with improved graphic quality and performance.)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex); Atomic Physics (physics.atom-ph)
[119]  arXiv:1712.04283 (replaced) [pdf, ps, other]
Title: Refutation of [Chyba and Hand, Phys. Rev. Applied 6, 014017 (2016)]: No Electric Power can be Generated from Earth's Rotation through its Own Magnetic Field
Authors: J. Jeener
Comments: 4 pages, minor revisions, submitted to Phys. Rev. Applied as a Comment
Subjects: Applied Physics (physics.app-ph)
[120]  arXiv:1712.04610 (replaced) [pdf, other]
Title: Data-driven localization mappings in filtering the monsoon-Hadley multicloud convective flows
Comments: monthly weather review (in press)
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Computational Physics (physics.comp-ph)
[121]  arXiv:1712.05924 (replaced) [pdf]
Title: Nonlinear Instability Modelling of a Nonlocal Strain Gradient Functionally Graded Capacitive Nano-Bridge Under van der Waals force in Thermal Environment
Subjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[122]  arXiv:1712.05948 (replaced) [pdf, other]
Title: Towards compact Free Electron Laser based on laser plasma accelerators
Authors: ME Couprie
Comments: 13 pages, 8 fig
Subjects: Accelerator Physics (physics.acc-ph)
[123]  arXiv:1712.09206 (replaced) [pdf, other]
Title: Chaos-guided Input Structuring for Improved Learning in Recurrent Neural Networks
Comments: 11 pages with 5 figures including supplementary material
Subjects: Neurons and Cognition (q-bio.NC); Neural and Evolutionary Computing (cs.NE); Biological Physics (physics.bio-ph)
[124]  arXiv:1801.02666 (replaced) [pdf, other]
Title: Increased sensitivity of spin noise spectroscopy using homodyne detection in $n$-doped GaAs
Comments: 9 pages, 4 figures, Minor revisions, New References
Subjects: Instrumentation and Detectors (physics.ins-det); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
[125]  arXiv:1801.06530 (replaced) [pdf, other]
Title: In-water chemical sensing by fiber-optic evanescent waves spectroscopy using mid-infrared quantum cascade lasers
Journal-ref: Sensors and Actuators B: Chemical 262 (2018) 195-199
Subjects: Applied Physics (physics.app-ph); Instrumentation and Detectors (physics.ins-det)
[126]  arXiv:1801.07652 (replaced) [pdf, other]
Title: Vorticity and helicity decompositions and dynamics with Real Schur form of the velocity gradient
Authors: Jian-Zhou Zhu
Comments: quartet resonance analysis is outlined
Subjects: Fluid Dynamics (physics.flu-dyn); Chaotic Dynamics (nlin.CD); Geophysics (physics.geo-ph)
[127]  arXiv:1801.08698 (replaced) [pdf, ps, other]
Title: Average values of functionals and concentration without measure
Authors: Cheng-shi Liu
Comments: 32 pages
Subjects: Probability (math.PR); Mathematical Physics (math-ph); Functional Analysis (math.FA); Statistics Theory (math.ST); Data Analysis, Statistics and Probability (physics.data-an)
[128]  arXiv:1801.09492 (replaced) [pdf, ps, other]
Title: Effects of heterogeneity in power-grid network models
Comments: 9 pages, 10 Figures, results recalculated following K/N -&gt; K/N_i coupling renormalization
Subjects: Physics and Society (physics.soc-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
[129]  arXiv:1802.01524 (replaced) [pdf, other]
Title: Diffraction of a CW atom laser in the Raman-Nath regime
Comments: 5 pages and 3 figures
Subjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
[130]  arXiv:1802.03722 (replaced) [pdf, ps, other]
Title: Influence of pulsatile blood flow on allometry of aortic wall shear stress
Comments: 10 pages, 4 figures
Subjects: Biological Physics (physics.bio-ph); Fluid Dynamics (physics.flu-dyn); Tissues and Organs (q-bio.TO)
[131]  arXiv:1802.04395 (replaced) [pdf, other]
Title: Spatially-resolved Fluorescence-detected Two-dimensional Electronic Spectroscopy Probes Varying Electronic Couplings in Photosynthetic Bacteria
Comments: Submitted to Nature Communications on Feb 12th, 2018, acknowledgements, and author contributions updated in version 2
Subjects: Chemical Physics (physics.chem-ph); Biological Physics (physics.bio-ph)
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